Detection of Novel BEST1 Variations in Autosomal Recessive Bestrophinopathy Using Third-generation Sequencing

Objective:Autosomal recessive bestrophinopathy(ARB),a retinal degenerative disease,is characterized by central visual loss,yellowish multifocal diffuse subretinal deposits,and a dramatic decrease in the light peak on electrooculogram.The potential pathogenic mechanism involves mutations in the BEST1 gene,which encodes Ca2+-activated Cl−channels in the retinal pigment epithelium(RPE),resulting in degeneration of RPE and photoreceptor.In this study,the complete clinical characteristics of two Chinese ARB families were summarized.Methods:Pacific Biosciences(PacBio)single-molecule real-time(SMRT)sequencing was performed on the probands to screen for disease-causing gene mutations,and Sanger sequencing was applied to validate variants in the patients and their family members.Results:Two novel mutations,c.202T>C(chr11:61722628,p.Y68H)and c.867+97G>A,in the BEST1 gene were identified in the two Chinese ARB families.The novel missense mutation BEST1 c.202T>C(p.Y68H)resulted in the substitution of tyrosine with histidine in the N-terminal region of transmembrane domain 2 of bestrophin-1.Another novel variant,BEST1 c.867+97G>A(chr11:61725867),located in intron 7,might be considered a regulatory variant that changes allele-specific binding affinity based on motifs of important transcriptional regulators.Conclusion:Our findings represent the first use of third-generation sequencing(TGS)to identify novel BEST1 mutations in patients with ARB,indicating that TGS can be a more accurate and efficient tool for identifying mutations in specific genes.The novel variants identified further broaden the mutation spectrum of BEST1 in the Chinese population.

Novel Pathogenic Mutation of PNPLA1 Identified in Autosomal Recessive Congenital Ichthyosis:A Case Report

Autosomal recessive congenital ichthyosis(ARCI)is characterized by being born as collodion babies,hyperkeratosis,and skin scaling.We described a collodion baby at birth with mild ectropion,eclabium,and syndactyly.Whole exome sequencing showed a compound heterozygous variant c.[56C>A],p.(Ser19X)and c.[100G>A],p.(Ala34Thr)in the PNPLA1 gene[NM_001145717;exon 1].The protein encoded by PNPLA1 acts as a unique transacylase that specifically transfers linoleic acid from triglyceride toω-hydroxy fatty acid in ceramide,thus giving rise toω-O-acylceramide,a particular class of sphingolipids that is essential for skin barrier function.The variant was located in the patatin core domain of PNPLA1 and resulted in a truncated protein which could disrupt the function of the protein.This case report highlights a novel compound heterozygous mutation in PNPLA1 identified in a Chinese child.

Autosomal recessive hereditary auditory neuropathy

Objectives: Auditory neuropathy (AN) is a sensorineural hearing disorder characterized by absent or abnormal auditory brainstem responses (ABRs) and normal cochlear outer hair cell function as measured by otoacoustic emissions (OAEs). Many risk factors are thought to be involved in its etiology and pathophysiology. Three Chinese pedigrees with familial AN are presented herein to demonstrate involvement of genetic factors in AN etiology. Methods: Probands of the above - mentioned pedigrees, who had been diagnosed with AN, were evaluated and followed up in the Department of Otolaryngology Head and Neck Surgery, China PLA General Hospital. Their family members were studied and the pedigree diagrams were established. History of illness, physical examination,pure tone audiometry, acoustic reflex, ABRs and transient evoked and distortion- product otoacoustic emissions (TEOAEs and DPOAEs) were obtained from members of these families. DPOAE changes under the influence of contralateral sound stimuli were observed by presenting a set of continuous white noise to the non - recording ear to exam the function of auditory efferent system. Some subjects received vestibular caloric test, computed tomography (CT)scan of the temporal bone and electrocardiography (ECG) to exclude other possible neuropathy disorders. Results: In most affected subjects, hearing loss of various degrees and speech discrimination difficulties started at 10 to16 years of age. Their audiological evaluation showed absence of acoustic reflex and ABRs. As expected in AN, these subjects exhibited near normal cochlear outer hair cell function as shown in TEOAE & DPOAE recordings. Pure- tone audiometry revealed hearing loss ranging from mild to severe in these patients. Autosomal recessive inheritance patterns were observed in the three families. In Pedigree Ⅰ and Ⅱ, two affected brothers were found respectively, while in pedigree Ⅲ, 2 sisters were affected. All the patients were otherwise normal without evidence of peripheral neuropathy at the time of this writing. Conclusions: In this study, patients with feature of non- syndromic hereditary auditory neuropathy were identified in three Chinese families.Pedigree analysis indicates autosomal recessive inheritances in the pedigrees. The observed inheritance and clinical audiologic findings are different from those previously described for non-syndromic low-frequency sensorineural hearing loss. This information should facilitate future molecular candidate genes screening for understanding the mechanism of AN.

Homozygous Nonsense Mutation in SDR9C7 in a Chinese Patient With Autosomal Recessive Congenital Ichthyosis

Introduction:Autosomal recessive congenital ichthyosis(ARCI)is a heterogeneous group of cornification disorders.To date,14 genes have been found to be related to ARCI.Case presentation:A 23-year-old woman developed generalized erythroderma and scales over her trunk and limbs shortly after birth,followed by recurrent blisters and nail deformities.A diagnosis of ARCI was made based on her clinical manifestations,family history,and genetic analysis,which revealed a homozygous mutation inSDR9C7(c.187C>T,p.Q63X).Discussion:Most genes responsible for ARCI are associated with epidermal lipid metabolism,which contributes to the cutaneous barrier.SDR9C7,which encodes short-chain dehydrogenase/reductase family 9C member 7,has also been recently found to play vital roles in this process by regulating ceramide binding to the epidermal cornified cell envelope.For patients clinically suspected to have ARCI,recurrent onychomycosis is a strong indication that they carry aSDR9C7 gene mutation.Conclusion:Remarkable phenotypic and genotypic heterogeneity exists among patients with ARCI.Genetic analysis is an effective tool in diagnosing this and other hereditary diseases.Our patient developed recurrent onychomycosis,a typical presentation of ARCI caused bySDR9C7 mutation,and the unusual blisters further expand the clinical phenotypic spectrum of ARCI.

Exome sequencing identifies compound heterozygous PKHD1 mutations as a cause of autosomal recessive polycystic kidney disease

Background Autosomal recessive polycystic kidney disease （ARPKD） is a rare inherited disease, which is a disorder with multiple organ involvement, mainly the kidney and liver. It is caused by mutations in the PKHD1 gene. Here, we reported the clinical characteristics of a case with ARPKD and analyze the genetic features of this patient as well as of his father using targeted exome sequencing and Sanger sequencing. Methods Genomic DNA was extracted from peripheral blood leukocytes obtained from a patient with ARPKD. The mutations were identified using exome sequencing and confirmed by Sanger sequencing. Results The patient was diagnosed as ARPKD based on ultrasonography and abdominal computed tomography which showed polycystic changes, multiple calcinosis of both kidneys, and multiple dilated bile ducts of the liver. Compound heterozygous PKHD1 gene mutations A979G and G5935A, which lead to substitution of an asparagine for an aspartate at amino acid 327 （N327D） and a glycine for an arginine at amino acid 1979 （G1979R） respectively, were identified using targeted exome sequencing and confirmed by Sanger sequencing for the patient. In addition, the father of the patient was identified to be a carrier of heterozygous A979G mutation of this gene. Conclusions We identified that the compound heterozygous PKHD1 gene mutations are the molecular basis of the patient with ARPKD. Targeted exome sequencing is suitable for genetic diagnosis of single-gene inherited diseases like ARPKD in which the pathogenic gene is a large.

Genetic spectrum and clinical features in a cohort of Chinese patients with autosomal recessive cerebellar ataxias

Background:Although many causative genes have been uncovered in recent years,genetic diagnosis is still missing for approximately 50%of autosomal recessive cerebellar ataxia(ARCA)patients.Few studies have been performed to determine the genetic spectrum and clinical profile of ARCA patients in the Chinese population.Methods:Fifty-four Chinese index patients with unexplained autosomal recessive or sporadic ataxia were investigated by whole-exome sequencing(WES)and copy number variation(CNV)calling with ExomeDepth.Likely causal CNV predictions were validated by CNVseq.Results:Thirty-eight mutations including 29 novel ones were identified in 25 out of the 54 patients,providing a 46.3%positive molecular diagnostic rate.Ten different genes were involved,of which four most common genes were SACS,SYNE1,ADCK3 and SETX,which accounted for 76.0%(19/25)of the positive cases.The de novo microdeletion in SACS was reported for the first time in China and the uniparental disomy of ADCK3 was reported for the first time worldwide.Clinical features of the patients carrying SACS,SYNE1 and ADCK3 mutations were summarized.Conclusions:Our results expand the genetic spectrum and clinical profiles of ARCA patients,demonstrate the high efficiency and reliability of WES combined with CNV analysis in the diagnosis of suspected ARCA,and emphasize the importance of complete bioinformatics analysis of WES data for accurate diagnosis.

Autosomal recessive cerebellar ataxia with spasticity due to a rare mutation in GBA2 gene in a large consanguineous Saudi family

The nonlysosomal glucosylceramidase b2(GBA2)gene encode an enzyme that catalyzes the hydrolysis of glucosylceramide to glucose and ceramide.Mutations in the GBA2 gene have been reported to cause hereditary spastic paraplegia,autosomal recessive cerebellar ataxia with spasticity,and Marinescu-Sjogren-Like Syndrome.In this study,we report the clinical features and genetic diagnosis of autosomal recessive cerebellar ataxia with spasticity due to a rare mutation in GBA2 gene in a large consanguineous Saudi family.We included a large consanguineous Saudi family with a presumptive clinical diagnosis of ataxia at King Abdulaziz Medical City in Jeddah,Saudi Arabia.The family included six affected individuals and four unaffected in addition to the parents.Whole exome sequencing(WES)was performed for the probandⅣ-5,and Sanger sequencing was used to confirm the variant in other family members.Segregation study was performed using DNA from the parents and siblings of the proband.Sequence analysis identified a homozygous variant c.2618G>A,p.(Arg873His)in GBA2 gene.The homozygous variant was identified in affected members of the family while the parents and the other four siblings were heterozygous carriers of the variant.One sibling was not available for genetic testing.The variant identified in our patients is classified as pathogenic considering the current evidence of the variant.Autosomal recessive cerebellar ataxia with spasticity is an extremely rare genetic disorder with very few cases reported in the literature.We conclude that the c.2617G>A mutation in GBA2 gene causes the loss of function with abolishment of the enzymatic activity that causes the disease.This report adds further evidence to support the pathogenicity of this variant.The patients had the classical clinical phenotype of cerebellar ataxia and spasticity consistent with previous reports in the literature.

3M syndrome patient with a novel mutation:A case rep

BACKGROUND A rare autosomal recessive genetic disorder,3M syndrome,is characterized by severe intrauterine and postnatal growth retardation.Children with 3M syndrome typically exhibit short stature,facial deformities,long tubular bones,and high vertebral bodies but generally lack mental abnormalities or other organ damage.Pathogenic genes associated with 3M syndrome include CUL7,OBSL1 and CCDC8.The clinical and molecular characteristics of patient with 3M syn-drome are unique and serve as important diagnostic indicators.CASE SUMMARY In this case,the patient displayed square shoulders,scoliosis,long slender tubular bones,and normal neurological development.Notably,the patient did not exhibit the typical dysmorphic facial features,relative macrocephaly,or growth retardation commonly observed in individuals with 3M syndrome.Whole exon sequencing revealed a novel heterozygous c.56681+1G>C(Splice-3)variant and a previously reported nonsense heterozygous c.3341G>A(p.Trp1114Ter)variant of OBSL1.Therefore,it is important to note that the clinical features of 3M syndrome may not always be observable,and genetic confirmation is often required.Additionally,the identification of the c.5683+1G>C variant in OBSL1 is notewor-thy because it has not been previously reported in public databases.CONCLUSION Our study identified a new variant(c.5683+1G>C)of OBSL1 that contributes to expanding the molecular profile of 3M syndrome.

Nucleus-targeted Dmp1 transgene fails to rescue dental defects in Dmp1 null mice

Dentin matrix protein 1（DMP1） is essential to odontogenesis. Its mutations in human subjects lead to dental problems such as dental deformities, hypomineralization and periodontal impairment. Primarily, DMP1 is considered as an extracellular matrix protein that promotes hydroxyapatite formation and activates intracellular signaling pathway via interacting with avb3 integrin. Recent in vitro studies suggested that DMP1 might also act as a transcription factor. In this study, we examined whether full-length DMP1 could function as a transcription factor in the nucleus and regulate odontogenesis in vivo. We first demonstrated that a patient with the DMP1M1 V mutation, which presumably causes a loss of the secretory DMP1 but does not affect the nuclear translocation of DMP1, shows a typical rachitic tooth defect. Furthermore, we generated transgenic mice expressingNLSDMP1, in which the endoplasmic reticulum（ER） entry signal sequence of DMP1 was replaced by a nuclear localization signal（NLS） sequence, under the control of a 3.6 kb rat type I collagen promoter plus a 1.6 kb intron 1. We then crossbred theNLSDMP1 transgenic mice with Dmp1 null mice to express the NLSDMP1 in Dmp1-deficient genetic background. Although immunohistochemistry demonstrated thatNLSDMP1 was localized in the nuclei of the preodontoblasts and odontoblasts, the histological, morphological and biochemical analyses showed that it failed to rescue the dental and periodontal defects as well as the delayed tooth eruption in Dmp1 null mice. These data suggest that the full-length DMP1 plays no apparent role in the nucleus during odontogenesis.

Combined liver and kidney transplantation in children and long-term outcome

Combined liver-kidney transplantation(CLKT)is a rarely performed complex surgical procedure in children and involves transplantation of kidney and either whole or part of liver donated by the same individual(usually a cadaver)to the same recipient during a single surgical procedure.Most common indications for CLKT in children are autosomal recessive polycystic kidney disease and primary hyperoxaluria type 1.Atypical haemolytic uremic syndrome,methylmalonic academia,and conditions where liver and renal failure co-exists may be indications for CLKT.CLKT is often preferred over sequential liver-kidney transplantation due to immunoprotective effects of transplanted liver on renal allograft;however,liver survival has no significant impact.Since CLKT is a major surgical procedure which involves multiple and complex anastomosis surgeries,acute complications are not uncommon.Bleeding,thrombosis,haemodynamic instability,infections,acute cellular rejections,renal and liver dysfunction are acute complications.The long-term outlook is promising with over 80%5-year survival rates among those children who survive the initial six-month postoperative period.

Possible PKHD1 Hot-spot Mutations Related to Early Kidney Function Failure or Hepatofibrosis in Chinese Children with ARPKD:A Retrospective Single Center Cohort Study and Literature Review

PKHD1 mutations are generally considered to cause autosomal recessive polycystic kidney disease(ARPKD).ARPKD is a rare disorder and one o f the most severe conditions leading to end-stage renal disease in childhood.With the biallelic deletion mutation,patients have difficulty in surviving the perinatal period,resulting in perinatal or neonatal death.This study retrospectively analyzed patient characteristics,imaging characteristics,laboratory examinations and family surveys from 7 Chinese children with different PKHD1 gene mutations diagnosed by high-throughput sequencing from January 2014 to February 2018.O f the 7 children,there were 3 males and 4 females.Eight missense mutations,two frameshift mutations,two deletion mutations,and two intronic slicing mutations were identified.Six of the mutations have not previously been identified.In the literature search,we identified a total of 29 Chinese children with PKHD1 mutations.The missense mutation c.2507T>C in exon 24 was found in one patient in our study,and five patients with liver fibrosis but normal renal function were reported in the literature.The missense mutation c.5935G>A in exon 37 was found in two patients in our study and three cases in the literature.Four patients had renal failure at an age as young as 1 year of those five patients with the missense mutation c.5935G>A in exon 37.It was concluded that:(1)Kidney length more than 2-3 SDs above the mean and early-onset hypertension might be associated with PKHDI-associated ARPICD;(2)The more enlarged the kidney size is,the lower the renal function is likely to be;(3)c.5935G>A may be a hot spot that leads to early renal failure in Chinese children with PKHD1 mutations;(4)c.2507T>C may be a hot-spot mutation associated with hepatic lesions in Chinese children with PKHD1.

Novel mutations in PDE6A and CDHR1 cause retinitis pigmentosa in Pakistani families

AIM:To investigate the genetic basis of autosomal recessive retinitis pigmentosa(arRP)in two consanguineous/endogamous Pakistani families.METHODS:Whole exome sequencing(WES)was performed on genomic DNA samples of patients with arRP to identify disease causing mutations.Sanger sequencing was performed to confirm familial segregation of identified mutations,and potential pathogenicity was determined by predictions of the mutations’functions.RESULTS:A novel homozygous frameshift mutation[NM_000440.2:c.1054delG,p.(Gln352Argfs*4);Chr5:g.149286886del(GRCh37)]in the PDE6A gene in an endogamous family and a novel homozygous splice site mutation[NM_033100.3:c.1168-1G>A,Chr10:g.85968484G>A(GRCh37)]in the CDHR1 gene in a consanguineous family were identified.The PDE6A variant p.(Gln352Argfs*4)was predicted to be deleterious or pathogenic,whilst the CDHR1 variant c.1168-1G>A was predicted to result in potential alteration of splicing.CONCLUSION:This study expands the spectrum of genetic variants for arRP in Pakistani families.

Whole-genome amplification/preimplantation genetic testing for propionic acidemia of successful pregnancy in an obligate carrier Mexican couple:A case report

BACKGROUND Identifying a potential single monogenetic disorder in healthy couples is costly due to the Assisted Reproduction facilities'current methodology for screening,which focuses on the detecting multiple genetic disorders at once.Here,we report the successful application of a low-cost and fast preimplantation genetic testing for monogenic/single gene defects(PGT-M)approach for detecting propionic acidemia(PA)in embryos obtained from a confirmed heterozygous propionyl-CoA carboxylase alpha subunit(PCCA)couple.CASE SUMMARY A fertile 32-years old Mexican couple with denied consanguinity sought antenatal genetic counseling.They were suspected obligate PA carriers due to a previous deceased PA male newborn with an unknown PCCA/propionyl-CoA carboxylase beta subunit(PCCB)genotype.Next-Generation Sequencing revealed a heterozygous genotype for a pathogenic PCCA variant(c.2041-1G>T,ClinVar:RCV-000802701.1;dbSNP:rs1367867218)in both parents.The couple requested in vitro fertilization(IVF)and PGT-M for PA.From IVF,12 oocytes were collected and fertilized,of which two resulted in high-quality embryos.Trophectoderm biopsies and Whole Genome Amplification by a fragmentation/amplification-based method were performed and revealed that the two embryos were euploid.Endpoint polymerase chain reaction and further Sanger sequencing of the exon-intron borders revealed a wild-type PCCA male embryo and a heterozygous c.2041-1G>T female embryo.Both embryos were transferred,resulting in a clinical pregnancy and the delivery of a healthy male newborn(38 wk,weight:4080 g,length:49 cm,APGAR 9/9).The absence of PA was confirmed by expanded newborn screening.CONCLUSION We show that using PGT-M with Whole Genome Amplification templates,coupled with IVF,can reduce the transmission of a pathogenic variant of the PCCA gene.

Megalencephalic Leukoencephalopathy with Subcortical Cysts-a New Child Leukoencephalopathy

Here we review a new variety of leukoencephalopathy with infantile megalencephaly and discrepant clinical course (MLC, MIM: 604004). These children had megalencephaly in the first year of life, with or without mild delay of motor function and/or seizures. After a few years, motor handicap was slowly progressive with unsteady gait, serious cerebellar ataxia and mild plasticity. Eventually most of patients were confined to a wheelchair. Meanwhile mental development was relatively preserved, although the learning problems was increased from the midway of elementary school. Most of patients had tonic-clonic seizure and some might advance to status epilepticus. Antiepileptic drugs may effectively control seizure. The disorders of known metabolic defects were excluded. Neurophysiological examination showed that EEG had interictal epileptic discharges on the generalized slow wave background in most patients. The cerebral white matter had diffuse abnormality, with swelling of white matter, and cysts in the frontoparietal and anterior-temporal lobes on MRI examination. Some central white matter structures were spared, such as corpus callosum. The severity of lesions on MRI is inconsistent with the clinical signs. Pathogenesis of this disease was unknown. The pathological findings found a spongiform leukoencephalopathy due to myelin splitting and intramyelinic vacuole formation but without myelin loss. This disease had probably an autosomal recessive inheritance. The gene KIAA027 on 22qtel was responsible for MLC.

Clinical features and genetic spectrum in Chinese patients with recessive hereditary spastic paraplegia

Background:Although many causative genes of hereditary spastic paraplegia(HSP)have been uncovered in recent years,there are still approximately 50% of HSP patients without genetically diagnosis,especially in autosomal recessive(AR)HSP patients.Rare studies have been performed to determine the genetic spectrum and clinical profiles of recessive HSP patients in the Chinese population.Methods:In this study,we investigated 24 Chinese index AR/sporadic patients by targeted next-generation sequencing(NGS),Sanger sequencing and multiplex ligation-dependent probe amplification(MLPA).Further functional studies were performed to identify pathogenicity of those uncertain significance variants.Results:We identified 11 mutations in HSP related genes including 7 novel mutations,including two(p.V1979_L1980delinsX,p.F2343 fs)in SPG11,two(p.T55 M,p.S308 T)in AP5Z1,one(p.S242N)in ALDH18A1,one(p.D597fs)in GBA2,and one(p.Q486X)in ATP13A2 in 8 index patients and their family members.Mutations in ALDH18A1,AP5Z1,CAPN1 and ATP13A2 genes were firstly reported in the Chinese population.Furthermore,the clinical phenotypes of the patients carrying mutations were described in detail.The mutation(p.S242 N)in ALDH18A1 decreased enzyme activity of P5CS and mutations(p.T55 M,p.S308 T)in AP5Z1 induced lysosomal dysfunction.Conclusion:Our results expanded the genetic spectrum and clinical profiles of AR-HSP patients and further demonstrated the efficiency and reliability of targeted NGS diagnosing suspected HSP patients.

A case report of microcephaly and refractory West syndrome associated with WDR62 mutation

The autosomal recessive form of primary microcephaly(MCPH)is a rare disorder characterized by microcephaly with variable degree of intellectual disability.WDR62 has been reported as the second causative gene of MCPH2.West syndrome is a severe epilepsy syndrome composed of the triad of spasms,hypsarrhythmia,and mental retardation.There are limited clinical reports regarding WDR62 mutation and West syndrome.Here we report a boy who was identified with WDR62 mutation and was followed up from age 3 months to 5 months and 14 days.He had the first seizure as the classic epileptic spasm at the age of 3 months.Psychomotor retardation was noted before the seizure occurred.The head circumference was 38.5 cm(SD 2.6)when he was 4 months old,no dysmorphic facial features were observed.He couldn’t support his head steadily or turn over.He was able to laugh when tricked by the parents,but couldn’t track the sound and light.At the early stage,the electroencephalogram showed multifocal discharges,which evolved into hypsarrhythmia one month later,and brain MRI showed developmental malformation of cerebral gyrus.Two heterozygous mutations were identified in WDR62 by whole exome sequencing c.1535G>A,p.R512Q and c.2618dupT,p.K874Qfs40.The patient was administrated with oral sodium valproate,nitrazepam,intramuscular adrenocorticotropic hormone for 2 weeks,and followed by prednisone,levetiracetam,topiramate and vigabatrin.However,there was no significant improvement on the seizure control after these treatments.According to the genetic report and clinical manifestation,we speculated that the WDR62 compound heterozygous mutation is responsible for the serious clinical phenotype.

Panoramic variation analysis of a family with neurodevelopmental disorders caused by biallelic loss-of-function variants in TMEM141,DDHD2,and LHFPL5

Highly clinical and genetic heterogeneity of neurodevelopmental disorders presents a major challenge in clinical genetics and medicine.Panoramic variation analysis is imperative to analyze the disease phenotypes resulting from multilocus genomic variation.Here,a Pakistani family with parental consanguinity was presented,characterized with severe intellectual disability(ID),spastic paraplegia,and deafness.Homozygosity mapping,integrated single nucleotide polymorphism(SNP)array,whole-exome sequencing,and whole-genome sequencing were performed,and homozygous variants in TMEM141(c.270G>A,p.Trp90^(*)),DDHD2(c.411+767_c.1249-327del),and LHFPL5(c.250delC,p.Leu84^(*))were identified.A Tmem141^(p.Trp90^(*)/p.Trp90^(*))mouse model was generated.Behavioral studies showed impairments in learning ability and motor coordination.Brain slice electrophysiology and Golgi staining demonstrated deficient synaptic plasticity in hippocampal neurons and abnormal dendritic branching in cerebellar Purkinje cells.Transmission electron microscopy showed abnormal mitochondrial morphology.Furthermore,studies on a human in vitro neuronal model(SH-SY5Y cells)with stable shRNA-mediated knockdown of TMEM141 showed deleterious effect on bioenergetic function,possibly explaining the pathogenesis of replicated phenotypes in the cross-species mouse model.Conclusively,panoramic variation analysis revealed that multilocus genomic variations of TMEM141,DDHD2,and LHFPL5 together caused variable phenotypes in patient.Notably,the biallelic loss-of-function variants of TMEM141 were responsible for syndromic ID.