New recessive compound heterozygous variants of RP1L1 in RP1L1 maculopathy

AIM:To identify a maculopathy patient caused by new recessive compound heterozygous variants in RP1L1.METHODS:Comprehensive retinal morphological and functional examinations were evaluated for the patient with RP1L1 maculopathy.Targeted sequence capture array technique was used to screen potential pathologic variants.Polymerase chain reaction and Sanger sequencing were used to confirm the screening results.RESULTS:Fundus examination showed round macular lesions appeared in both eyes.Optical coherence tomography showed that the inner segment/outer segment continuity was disorganized and disruptive in the left eye,but it was uneven and slightly elevated in the right eye.Fundus autofluorescence showed patchy hyper-autofluorescence in the macula.Visual field examination indicates central defects in both eyes.Electroretinogram(ERG)and multifocal ERG showed no obvious abnormalities.Fundus fluorescein angiography in the macula showed obviously irregular hyper-fluorescence in the right eye and slightly hyper-fluorescence in the left eye.We found that the proband carried a missense variant(c.1972C>T)and a deletion variant(c.4717_4718del)of RP1L1,which were originated from the parents and formed compound heterozygous variants.Both variants are likely pathogenic according to the ACMG criteria.Multimodal imaging,ERG and detailed medical history are important diagnostic tools for differentiating between acquired and inherited retinal disorders.CONCLUSION:A maculopathy case with detailed retinal phenotype and new recessive compound heterozygous variants of RP1L1 is identified in a Chinese family,which expands the understanding of phenotype and genotype in RP1L1 maculopathy.

Compound heterozygous mutations in tripeptidyl peptidase 1 cause rare autosomal recessive spinocerebellar ataxia type 7:A case report

BACKGROUND Spinocerebellar ataxia recessive type 7(SCAR7)is a rare clinical manifestation beginning in childhood or adolescence.SCAR7 is caused by tripeptidyl peptidase 1(TPP1)gene mutations,and presents with cerebellar ataxia,pyramidal signs,neurocognitive impairment,deep paresthesia,and cerebellar atrophy.CASE SUMMARY Here,we describe a 25-year-old female patient in China who presented with increasing difficulty walking,falling easily,shaking limbs,instability holding items,slurred speech,coughing when drinking,palpitations,and frequent hunger and overeating.Magnetic resonance imaging showed cerebellar atrophy.Whole exome sequencing detected two compound heterozygous mutations in the TPP1 gene:c.1468G>A p.Glu490Lys and c.1417G>A p.Gly473Arg.Considering the patient’s clinical presentation and genetic test results,we hypothesized that complex heterozygous mutations cause TPP1 enzyme deficiency,which may lead to SCAR7.CONCLUSION We report the first case of SCAR7 from China.We also identify novel compound heterozygous mutations in the TPP1 gene associated with SCAR7,expanding the range of known disease-causing mutations for SCAR7.

Novel compound heterozygous GPR56 gene mutation in a twin with lissencephaly:A case report

BACKGROUND Lissencephaly(LIS)is a malformation of cortical development with broad gyri,shallow sulci and thickened cortex characterized by developmental delays and seizures.Currently,20 genes have been implicated in LIS.However,GRP56-related LIS has never been reported.GRP56 is considered one of the causative genes for bilateral frontoparietal polymicrogyria.Here,we report a twin infant with LIS and review the relevant literature.The twins both carried the novel compound heterozygous GPR56 mutations.CASE SUMMARY A 5-mo-old female infant was hospitalized due to repeated convulsions for 1 d.The patient had a flat head deformity that manifested as developmental delays and a sudden onset of generalized tonic-clonic seizures at 5 mo without any causes.The electroencephalography was normal.Brain magnetic resonance imaging revealed a simple brain structure with widened and thickened gyri and shallow sulci.The white matter of the brain was significantly reduced.Patchy long T1 and T2 signals could be seen around the ventricles,which were expanded,and the extracerebral space was widened.Genetic testing confirmed that the patient carried the GPR56 gene compound heterozygous mutations c.228delC(p.F76fs)and c.1820_1821delAT(p.H607fs).The unaffected father carried a heterozygous c.1820_1821delAT mutation,and the unaffected mother carried a heterozygous c.228delC mutation.The twin sister carried the same mutations as the proband.The patient was diagnosed with LIS.CONCLUSION This is the first case report of LIS that is likely caused by mutations of the GPR56 gene.

Compound heterozygous mutation in two unrelated cases of Chinese spinal muscular atrophy patients

Background Infantile proximal spinal muscular atrophy （SMA） is a common autosomal recessive neuromuscular disorder. Approximately 90-95% cases of SMA result from homozygous deletion of survival motor neuron gene 1（SMN1） and 5% cases are caused by compound heterozygous mutation （a SMN1 deletion on one allele and a subtle mutation on the other allele）.Methods In this research, two unrelated patients were clinically diagnosed according to the criteria of proximal SMA. Genetic diagnosis was performed to detect the homozygous deletion of exon 7 of SMN1 by PCR-restriction fragment length polymorphism （RFLP） and genomic sequencing. Multiplex ligation-dependent probe amplification （MLPA） analysis was carried out to measure copy numbers of SMN1, SMN2 and neuronal apoptosis inhibitor protein （NAIP） in the patients. Further sequencing of SMN1allele-specific PCR （AS-PCR） and SMN1 clones were also performed to analyze the point mutation of SMN1 gene. Additionally,the pedigree analysis of these two families was carried out to identify the transmission of the mutation.Results The inconsistent results using PCR-RFLP and genomic sequencing showed homozygous deletion of exon 7 of SMN1 and heterozygous deletion accompanied with a suspicious mutation in SMN1 gene, respectively. MLPA analysis of these two cases exhibited one SMN1 copy deletion. One identical c.863G〉T （p. Arg288Met） mutation was found in two cases by sequencing the SMN1 clones, which confirmed that both cases were SMA compound heterozygotes. One case showed partial conversion to form hybrid SMN （SMN2 17/SMN1 E8） identified by clones sequencing and another case carrying 3 SMN2 implied complete conversion from SMN1 to SMN2.Conclusion p. Arg288Met is more a disease-causing mutation than a polymorphism variation, and children with this mutation may have more severe phenotypes.

R158Q and G212S,novel pathogenic compound heterozygous variants in SLC12A3 of Gitelman syndrome

The dysfunction of Na^(+)-Cl^(−)cotransporter(NCC)caused by mutations in solute carrier family12,member 3 gene(SLC12A3)primarily causes Gitelman syndrome(GS).In identifying the pathogenicity of R158Q and G212S variants of SLC12A3,we evaluated the pathogenicity by bioinformatic,expression,and localization analysis of two variants from a patient in our cohort.The prediction of mutant protein showed that p.R158Q and p.G212S could alter protein’s three-dimensional structure.Western blot showed a decrease of mutant Ncc.Immunofluorescence of the two mutations revealed a diffuse positive staining below the plasma membrane.Meanwhile,we conducted a compound heterozygous model—Ncc^(R156Q/G210S)mice corresponding to human NCC R158Q/G212S.Ncc^(R156Q/G210S)mice clearly exhibited typical GS features,including hypokalemia,hypomagnesemia,and increased fractional excretion of K^(+)and Mg^(2+)with a normal blood pressure level,which made Ncc^(R156Q/G210S)mice an optimal mouse model for further study of GS.A dramatic decrease and abnormal localization of the mutant Ncc in distal convoluted tubules contributed to the phenotype.The hydrochlorothiazide test showed a loss of function of mutant Ncc in Ncc^(R156Q/G210S)mice.These findings indicated that R158Q and G212S variants of SLC12A3 were pathogenic variants of GS.

First cases of MPV17 related mitochondrial DNA depletion syndrome with compound heterozygous mutations in p.R50Q/p.R50W:a case report

Mutations in MPV17 lead to severe mitochondrial DNA depletion syndrome(MTDPS).All known p.R50W variants in MPV17 are lethal.The homozygous variant p.R50Q in MPV17 among patients with Navajo neurohepatopathy is known to allow longer survival,although heterozygous variants p.R50Q have not been reported.This is the first clinical report in compound heterozygosity MPV17 mutation(p.R50W/p.R50Q).Three siblings were admitted due to multiple hepatic nodules;none presented neurological abnormalities.However,they suffered from severe hypoglycemia and cyclic vomiting.The diagnosis of MPV17-related MTDPS was confirmed by detection of a compound heterozygous MPV17 mutation(p.R50W/p.R50Q),and striking reduction of hepatic mitochondrial DNA.One patient developed pediatric-onset of hepatocellular carcinoma.Notably,all patients survived for extended periods,including two patients who received liver transplantation,which contrasted the high mortality rate associated with p.R50W mutations,as previously reported.The p.R50Q mutation might be associated with longer survival and improved liver transplantation outcomes.

Genetic Analysis of Two Novel GPI Variants Disrupting H Bonds and Localization Characteristics of 55 Gene Variants Associated with Glucose-6-phosphate Isomerase Deficiency

Objective:Glucose-6-phosphate isomerase(GPI)deficiency is a rare hereditary nonspherocytic hemolytic anemia caused by GPI gene variants.This disorder exhibits wide heterogeneity in its clinical manifestations and molecular characteristics,often posing challenges for precise diagnoses using conventional methods.To this end,this study aimed to identify the novel variants responsible for GPI deficiency in a Chinese family.Methods:The clinical manifestations of the patient were summarized and analyzed for GPI deficiency phenotype diagnosis.Novel compound heterozygous variants of the GPI gene,c.174C>A(p.Asn58Lys)and c.1538G>T(p.Trp513Leu),were identified using whole-exome and Sanger sequencing.The AlphaFold program and Chimera software were used to analyze the effects of compound heterozygous variants on GPI structure.Results:By characterizing 53 GPI missense/nonsense variants from previous literature and two novel missense variants identified in this study,we found that most variants were located in exons 3,4,12,and 18,with a few localized in exons 8,9,and 14.This study identified novel compound heterozygous variants associated with GPI deficiency.These pathogenic variants disrupt hydrogen bonds formed by highly conserved GPI amino acids.Conclusion:Early family-based sequencing analyses,especially for patients with congenital anemia,can help increase diagnostic accuracy for GPI deficiency,improve child healthcare,and enable genetic counseling.

Child with adenylosuccinate lyase deficiency caused by a novel complex heterozygous mutation in the ADSL gene:A case report

BACKGROUND Adenylosuccinate lyase(ADSL)deficiency is a rare autosomal-recessive defect of purine metabolism caused by mutation of the ADSL gene.It can cause severe neurological impairment and diverse clinical manifestations,including epilepsy.CASE SUMMARY Here,we describe a 3-year-old Chinese boy who had both psychomotor retardation and refractory epilepsy.Magnetic resonance imaging showed myelin hypoplasia.Electroencephalography findings supported a diagnosis of epilepsy.Whole-exon sequencing revealed the presence of a novel complex heterozygous mutation in the ADSL gene:The splicing mutation c.154-3C>G and the missense mutation c.71C>T(p.Pro24Leu).Considering the patient’s clinical presentation and genetic test results,the complex heterozygous mutation was predicted to prevent both ADSL alleles from producing normal ADSL,which may have led to ADSL deficiency.Finally,the child was diagnosed with ADSL deficiency.CONCLUSION We identified a novel complex heterozygous mutation in the ADSL gene associated with ADSL deficiency,thus expanding the known spectrum of pathogenic mutations that cause ADSL deficiency.Additionally,we describe epilepsy that occurs in patients with ADSL deficiency.

Crumbs homolog 2 mutation in two siblings with steroid-resistant nephrotic syndrome:Two case reports

BACKGROUND Crumbs homolog 2(CRB2)is a recently discovered gene that is closely related to the maintenance of normal polarity in podocytes;mutations can directly lead to steroid-resistant nephrotic syndrome(SRNS).However,the characteristics of nephrotic syndrome(NS)caused by CRB2 mutations have not been described.CASE SUMMARY We report a novel compound heterozygous mutation of the CRB2 gene in two siblings with SRNS.The two siblings had edema,proteinuria,hypoproteinemia and hyperlipidemia.Both their father and mother had normal phenotypes(no history of NS).Whole exon sequencing(WES)of the family showed a novel compound heterozygous mutation,c.2290(exon 8)C>T and c.3613(exon 12)G>A.Glucocorticoid therapy(methylprednisolone pulse therapy or oral prednisone)and immunosuppressive agents(tacrolimus)had no effect.During a 3-year follow-up after genetic diagnosis by WES,proteinuria persisted,but the patient was healthy.CONCLUSION CRB2 mutations related to SRNS often occur in exons 7,10,and 12.Clinical manifestations of SRNS caused by CRB2 mutations are often less severe than in other forms of SRNS.

Familial hemophagocytic lymphohistiocytosis type 2 in a female Chinese neonate:A case report and review of the literature

BACKGROUND Familial hemophagocytic lymphohistiocytosis type 2(FHL2)is a rare genetic disorder presenting with fever,hepatosplenomegaly,and pancytopenia secondary to perforin-1(PRF1)mutation.FLH2 has been described in Chinese but usually presents after 1 year old.We describe a female Chinese neonate with FHL2 secondary to compound heterozygous PRF1 mutation with symptom onset before 1 mo old.We review Chinese FHL2 patients in the literature for comparison.CASE SUMMARY A 15-d-old female neonate was referred to our hospital for persistent fever and thrombocytopenia with diffuse petechiae.She was born to a G5P3 mother at 39 wk and 4 d via cesarean section secondary to breech presentation.No resuscitation was required at birth.She was described to be very sleepy with poor appetite since birth.She developed a fever up to 39.5°C at 7 d of life.Leukocytosis,anemia,and thrombocytopenia were detected at a local medical facility CONCLUSION A literature review identified 75 Chinese FHL2 patients,with only five presenting in the first year of life.Missense and frameshift mutations are the most common PRF1 mutations in Chinese,with 24.8%having c.1349C>T followed by 11.6%having c.65delC.The c.658G>C mutation has only been reported once in the literature and our case suggests it can be pathogenic,at least in the presence of another pathogenic mutation such as c.1066C>T.

Autosomal recessive spinocerebellar ataxia type 4 with a VPS13D mutation:A case report

BACKGROUND Autosomal recessive spinocerebellar ataxia type 4(SCAR4)is a type of SCA that is a group of hereditary diseases characterized by gait ataxia.The main clinical features of SCAR4 are progressive cerebellar ataxia,pyramidal signs,neuropathy,and macrosaccadic intrusions.To date,many gene dysfunctions have been reported to be associated with SCAR4.CASE SUMMARY Here,we report a novel compound heterozygous mutation,c.3288delA(p.Asp1097-ThrfsTer6),in the VPS13D gene in a young female Chinese patient.The patient found something wrong with her legs about 10 years ago and presented with the typical characteristics of SCAR4 when she came to the hospital,including ataxia,neuropathy,and positive pyramidal signs.She was then diagnosed with SCAR4 and went home with symptomatic schemes.CONCLUSION SCAR4 is a hereditary disease characterized by ataxia,pyramidal signs,neuropathy,and macrosaccadic intrusions.We report a novel compound heterozygous mutation,c.3288delA(p.Asp1097ThrfsTer6),in the VPS13D gene,which enriches the gene mutation spectrum and provides additional information about SCAR4.

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.