Multiplex gene editing reduces oxalate production in primary hyperoxaluria type 1

Targeting key enzymes that generate oxalate precursors or substrates is an alternative strategy to eliminate primary hyperoxaluria type I(PH1),the most common and lifethreatening type of primary hyperoxaluria.The compact Clustered Regularly Interspaced Short Palindromic Repeats(CRISPR)from the Prevotella and Francisella 1(Cpf1)protein simplifies multiplex gene editing and allows for all-in-one adeno-associated virus(AAV)delivery.We hypothesized that the multiplex capabilities of the Cpf1system could help minimize oxalate formation in PH1 by simultaneously targeting the hepatic hydroxyacid oxidase 1(Hao1)and lactate dehydrogenase A(Ldha)genes.Study cohorts included treated PH1 rats(Agxt Q84X rats injected with AAV-AsCpf1 at 7 days of age),phosphate-buffered saline(PBS)-injected PH1 rats,untreated PH1 rats,and age-matched wild-type(WT)rats.The most efficient and specific CRISPR RNA(crRNA)pairs targeting the rat Hao1and Ldha genes were initially screened ex vivo.In vivo experiments demonstrated efficient genome editing of the Hao1 and Ldha genes,primarily resulting in small deletions.This resulted in decreased transcription and translational expression of Hao1 and Ldha.Treatment significantly reduced urine oxalate levels,reduced kidney damage,and alleviated nephrocalcinosis in rats with PH1.No liver toxicity,ex-liver genome editing,or obvious offtarget effects were detected.We demonstrated the AAVAsCpf1 system can target multiple genes and rescue the pathogenic phenotype in PH1,serving as a proof-ofconcept for the development of multiplex genome editingbased gene therapy.

A novel pathogenic splicing mutation of RPGR in a Chinese family with X-linked retinitis pigmentosa verified by minigene splicing assay

AIM:To report a novel splicing mutation in the RPGR gene(encoding retinitis pigmentosa GTPase regulator)in a three-generation Chinese family with X-linked retinitis pigmentosa(XLRP).METHODS:Comprehensive ophthalmic examinations including best corrected visual acuity,fundus photography,vision field,and pattern-visual evoked potential were performed to identify the disease phenotype of a six-yearold boy from the family(proband).Genomic DNA was extracted from peripheral blood of five available members of the pedigree.Whole-exome sequencing(WES),Sanger sequencing,and pSPL3-based exon trapping were used to investigate the aberrant splicing of RPGR.Human Splice Finder v3.1 and NNSPLICE v0.9 were used for in silico prediction of splice site variants.RESULTS:The proband was diagnosed as having retinitis pigmentosa(RP).He had severe symptoms with early onset.A novel splicing mutation,c.619+1G>C in RPGR was identified in the proband by WES and in four family members by Sanger sequencing.Minigene splicing assays verified that c.619+1G>C in RPGR would result in the formation of a damaging alternative transcript in which the last 91 bp of exon 6 were skipped,leading to the subsequent deletion of 623 correct amino acids(c.529_619del p.Val177Glnfs*16).CONCLUSION:We identify a novel splice donor site mutation causing aberrant splicing of RPGR.Our findings add to the catalog of pathological mutations of RPGR and further emphasize the functional importance of RPGR in RP pathogenesis and its complex clinical phenotypes.

Pathogenic mutations of TGFBI and CHST6 genes in Chinese patients with Avellino,lattice,and macular corneal dystrophies

Objective:To investigate gene mutations associated with three different types of corneal dystrophies(CDs),and to establish a phenotype-genotype correlation.Methods:Two patients with Avellino corneal dystrophy(ACD),four patients with lattice corneal dystrophy type I(LCD I) from one family,and three patients with macular corneal dystrophy type I(MCD I) were subjected to both clinical and genetic examinations.Slit lamp examination was performed for all the subjects to assess their corneal phenotypes.Genomic DNA was extracted from peripheral blood leukocytes.The coding regions of the human transforming growth factor β-induced(TGFBI) gene and carbohydrate sulfotransferase 6(CHST6) gene were amplified by polymerase chain reaction(PCR) and subjected to direct sequencing.DNA samples from 50 healthy volunteers were used as controls.Results:Clinical examination showed three different phenotypes of CDs.Genetic examination identified that two ACD subjects were associated with homozygous R124H mutation of TGFBI,and four LCD I subjects were all associated with R124C heterozygous mutation.One MCD I subject was associated with a novel S51X homozygous mutation in CHST6,while the other two MCD I subjects harbored a previously reported W232X homozygous mutation.Conclusions:Our study highlights the prevalence of codon 124 mutations in the TGFBI gene among the Chinese ACD and LCD I patients.Moreover,we found a novel mutation among MCD I patients.