Identification of novel pathogenic ABCA4 variants in a Han Chinese family with Stargardt disease

The ENG/VEGFα Pathway Is Likely Affected by a Nonsense Variant of Endoglin (ENG)/CD105, Causing Hereditary Hemorrhagic Telangiectasia Type 1 (HHT1) in a Chinese Family

Hereditary hemorrhagic telangiectasia (HHT), also called Rendu-Osler syndrome, is a group of rare genetic diseases characterized by autosomal dominance, multisystemic vascular dysplasia, and age-related penetrance. This includes arteriovenous malformations (AVMs) in the skin, brain, lung, liver, and mucous membranes. The correlations between the phenotype and genotype for HHT are not clear. An HHT Chinese pedigree was recruited. Whole exome sequencing (WES) analysis, Sanger verification, and co-segregation were conducted. Western blotting was performed for monitoring ENG/VEGFα signaling. As a result, a nonsense, heterozygous variant for ENG/CD105: c.G1169A:p. Trp390Ter of the proband with hereditary hemorrhagic telangiectasia type 1 (HHT1) was identified, which co-segregated with the disease in the M666 pedigree. Western blotting found that, compared with the normal levels associated with non-carrier family members, the ENG protein levels in the proband showed approximately a one-half decrease (47.4% decrease), while levels of the VEGFα protein, in the proband, showed approximately a one-quarter decrease (25.6% decrease), implying that ENG haploinsufficiency, displayed in the carrier of this variant, may affect VEGFα expression downregulation. Pearson and Spearman correlation analyses further supported TGFβ/ENG/VEGFα signaling, implying ENG regulation in the blood vessels. Thus, next-generation sequencing including WES should provide an accurate strategy for gene diagnosis, therapy, genetic counseling, and clinical management for rare genetic diseases including that in HHT1 patients.

Identification of novel compound heterozygous variants in the DNAH1 gene of a Chinese family with left-right asymmetry disorder

Most internal organs in humans and other vertebrates exhibit striking left-right asymmetry in position and structure. Variation of normal organ positioning results in left-right asymmetry disorders and presents as internal organ reversal or randomization. Up to date, at least 82 genes have been identified as the causative genetic factors of left-right asymmetry disorders. This study sought to discover potential pathogenic variants responsible for left-right asymmetry disorder present in a Han-Chinese family using whole exome sequencing combined with Sanger sequencing. Novel compound heterozygous variants, c.5690A>G (p.Asn1897Ser) and c.7759G>A (p.Val2587Met), in the dynein axonemal heavy chain 1 gene (DNAH1), were found in the proband and absent in unaffected family members. Conservation analysis has shown that the variants affect evolutionarily conserved residues, which may impact the tertiary structure of the DNAH1 protein. The novel compound heterozygous variants may potentially bear responsibility for left-right asymmetry disorder, which results from a perturbation of left-right axis coordination at the earliest embryonic development stages. This study broadens the variant spectrum of left-right asymmetry disorders and may be helpful for genetic counseling and healthcare management for the diagnosed individual, and promotes a greater understanding of the pathophysiology.

Novel compound heterozygous variants in the USH2A gene associated with autosomal recessive retinitis pigmentosa without hearing loss

Background: Retinitis pigmentosa (RP) is a group of progressive inherited retinal dystrophies characterized by the primary degeneration of rod photoreceptors and the subsequent loss of cone photoreceptors because of cell death. It is caused by different mechanisms, including inflammation, apoptosis, necroptosis, pyroptosis, and autophagy. Variants in the usherin gene (USH2A) have been reported in autosomal recessive RP with or without hearing loss. In the present study, we aimed to identify causative variants in a Han-Chinese pedigree with autosomal recessive RP. Methods: A six-member, three-generation Han-Chinese family with autosomal recessive RP was recruited. A full clinical examination, whole exome sequencing, and Sanger sequencing, as well as co-segregation analysis were performed. Results: Three heterozygous variants in the USH2A gene, c.3304C>T (p.Q1102*), c.4745T>C (p.L1582P), and c.14740G>A (p.E4914K), were identified in the proband, which were inherited from parents and transmitted to the daughters. Bioinformatics analysis supported the pathogenicity of the c.3304C>T (p.Q1102*) and c.4745T>C (p.L1582P) variants. Conclusions: Novel compound heterozygous variants in the USH2A gene, c.3304C>T (p.Q1102*) and c.4745T>C (p.L1582P), were identified as the genetic causes of autosomal recessive RP. The findings may enhance the current knowledge of the pathogenesis of USH2A-associated phenotypes, expand the spectrum of the USH2A gene variants, and contribute to improved genetic counseling, prenatal diagnosis, and disease management.

Identification of DNAH17 Variants in Han-Chinese Patients With Left–Right Asymmetry Disorders

The formation of left–right asymmetry of the visceral organs is a conserved feature of the human body, and the asymmetry specification of structure and function is precisely orchestrated by multiple regulatory mechanisms. The abnormal results of organ positioning situs arise from defective cilia structure or function during embryogenesis in humans. In this study, we recruited two unrelated Han-Chinese families with left–right asymmetry disorders. The combination of whole-exome sequencing and Sanger sequencing identified two compound heterozygous variants: c.4109C>T and c.9776C>T, and c.612C>G and c.8764C>T in the dynein axonemal heavy chain 17 gene (DNAH17) in two probands with left–right asymmetry disorders. We report for the first time a possible association between DNAH17 gene variants and left–right asymmetry disorders, which is known as a causal gene for asthenozoospermia. Altogether, the findings of our study may enlarge the DNAH17 gene variant spectrum in human left–right asymmetry disorders, pave a way to illustrate the potential pathogenesis of ciliary/flagellar disorders, and provide supplementary explanation for genetic counseling.

A BRCA1 Splice Site Variant Responsible for Familial Ovarian Cancer in a Han-Chinese Family

OBJECTIVE

Ovarian cancer (OC) is one of the most common and most lethal gynecological malignancies. OC has an age-dependent incidence and occurs more commonly in females older than 50 years old. Most OC patients are diagnosed at an advanced stage and have a poor prognosis. Germline mutations in the BRCA1 DNA repair associated gene (BRCA1) and the BRCA2 DNA repair associated gene (BRCA2) account for 20%-25% of epithelial ovarian cancer (EOC). BRCA1 germline mutations are more common in Chinese EOC patients.

METHODS

This study reported a three-generation Han-Chinese family containing four EOC patients and a rectal adenocarcinoma patient. Whole-exome sequencing was performed on two EOC patients and an unaffected individual. Variant validation was also performed in all available members by Sanger sequencing.

RESULTS

A heterozygous splice site variant, c.4358-2A>G in the BRCA1 gene, was identified. Bioinformatic analysis showed that the variant may change the splicing machinery.

CONCLUSION

The BRCA1 splice site variant, c.4358-2A>G was identified as the likely genetic cause for EOC, and may also be associated with the increased risk of rectal adenocarcinoma in the family. The findings were beneficial for genetic counseling, helpful for cancer prevention in other family members, and may facilitate therapy decision-making in the future to reduce cancer lethality.

Novel SCN5A and GPD1L Variants Identified in Two Unrelated Han-Chinese Patients With Clinically Suspected Brugada Syndrome

Brugada syndrome (BrS) is a complexly genetically patterned, rare, malignant, life-threatening arrhythmia disorder. It is autosomal dominant in most cases and characterized by identifiable electrocardiographic patterns, recurrent syncope, nocturnal agonal respiration, and other symptoms, including sudden cardiac death. Over the last 2 decades, a great number of variants have been identified in more than 36 pathogenic or susceptibility genes associated with BrS. The present study used the combined method of whole exome sequencing and Sanger sequencing to identify pathogenic variants in two unrelated Han-Chinese patients with clinically suspected BrS. Minigene splicing assay was used to evaluate the effects of the splicing variant. A novel heterozygous splicing variant c.2437-2A>C in the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) and a novel heterozygous missense variant c.161A>T [p.(Asp54Val)] in the glycerol-3-phosphate dehydrogenase 1 like gene (GPD1L) were identified in these two patients with BrS-1 and possible BrS-2, respectively. Minigene splicing assay indicated the deletion of 15 and 141 nucleotides in exon 16, resulting in critical amino acid deletions. These findings expand the variant spectrum of SCN5A and GPD1L, which can be beneficial to genetic counseling and prenatal diagnosis.

Novel MFSD8 Variants in a Chinese Family with Nonsyndromic Macular Dystrophy

Purpose

To identify the molecular etiology of a Chinese family with nonsyndromic macular dystrophy.

Methods

Ophthalmic examinations were performed, and genomic DNA was extracted from available family members. Whole exome sequencing of two members (the proband and her unaffected mother) and Sanger sequencing in available family members were performed to screen potential pathogenic variants.

Results

Novel compound heterozygous variants, c.1066C>T (p.Pro356Ser) and c.1102+2T>C, in the major facilitator superfamily domain containing 8 gene (MFSD8) were suspected to be involved in this family's macular dystrophy phenotype. The novel c.1066C>T variant in the MFSD8 gene probably resulted in substitution of serine for proline at the 356th residue and was predicted to be “uncertain significance” through in silico analyses. The novel c.1102+2T>C variant in the MFSD8 gene was likely to affect the splicing form and predicted to be “pathogenic.”

Conclusion

The novel compound heterozygous variants, c.1066C>T (p.Pro356Ser) and c.1102+2T>C, in the MFSD8 gene are likely responsible for the isolated macular dystrophy phenotype in this family. This study enlarged the MFSD8 gene mutant spectrum and might provide more accurate genetic counseling for this family.

Identification of compound heterozygous DNAH11 variants in a Han-Chinese family with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a group of genetically and clinically heterogeneous disorders with motile cilia dysfunction. It is clinically characterized by oto‐sino‐pulmonary diseases and subfertility, and half of the patients have situs inversus (Kartagener syndrome). To identify the genetic cause in a Han‐Chinese pedigree, whole‐exome sequencing was conducted in the 37‐year‐old proband, and then, Sanger sequencing was performed on available family members. Minigene splicing assay was applied to verify the impact of the splice‐site variant. Compound heterozygous variants including a splice‐site variant (c.1974‐1G>C, rs1359107415) and a missense variant (c.7787G>A, p.(Arg2596Gln), rs780492669), in the dynein axonemal heavy chain 11 gene (DNAH11) were identified and confirmed as the disease‐associated variants of this lineage. The minigene expression in vitro revealed that the c.1974‐1G>C variant could cause skipping over exon 12, predicted to result in a truncated protein. This discovery may enlarge the DNAH11 variant spectrum of PCD, promote accurate genetic counselling and contribute to PCD diagnosis.

A phase I clinical trial of human embryonic stem cell-derived retinal pigment epithelial cells for early-stage Stargardt macular degeneration: 5-years' follow-up

Objectives

To evaluate the long‐term biosafety and efficacy of transplantation of human embryonic stem cells‐derived retinal pigment epithelial (hESC‐RPE) cells in early‐stage of Stargardt macular degeneration (STGD1).

Materials and methods

Seven patients participated in this prospective clinical study, where they underwent a single subretinal transplantation of 1 × 10⁵ hESC‐RPE cells in one eye, whereas the fellow eye served as control. These patients were reassessed for a 60‐month follow‐up through systemic and ophthalmic examinations.

Results

None of the patients experienced adverse reactions systemically or locally, except for two who had transiently high intraocular pressure post‐operation. Functional assessments demonstrated that all of the seven operated eyes had transiently increased or stable visual function 1‐4 months after transplantation. At the last follow‐up visit, two of the seven eyes showed visual function loss than the baseline; however, one of them showed a stable visual acuity when compared with the change of fellow eye. Obvious small high reflective foci in the RPE layer were displayed after the transplantation, and maintained until the last visit. Interestingly, three categories of patients who were classified based on autofluorescence, exhibited distinctive patterns of morphological and functional change.

Conclusions

Subretinal transplantation of hESC‐RPE in early‐stage STGD1 is safe and tolerated in the long term. Further investigation is needed for choosing proper subjects according to the multi‐model image and function assessments.

Uncurtaining the pivotal role of ABC transporters in diabetes mellitus

The metabolic disorders are the edge points for the initiation of various diseases. These disorders comprised of several diseases including diabetes, obesity, and cardiovascular complications. Worldwide, the prevalence of these disorders is increasing day by day. The world's population is at higher threat of developing metabolic disease, especially diabetes. Therefore, there is an impregnable necessity of searching for a newer therapeutic target to reduce the burden of these disorders. Diabetes mellitus (DM) is marked with the dysregulated insulin secretion and resistance. The lipid and glucose transporters portray a pivotal role in the metabolism and transport of both of these. The excess production of lipid and glucose and decreased clearance of these leads to the emergence of DM. The ATP-binding cassette transporters (ABCT) are important for the metabolism of glucose and lipid. Various studies suggest the key involvement of ABCT in the pathologic process of different diseases. In addition, the involvement of other pathways, including IGF signaling, P13-Akt/PKC/MAPK signaling, and GLP-1 via regulation of ABCT, may help develop new treatment strategies to cope with insulin resistance dysregulated glucose metabolism, key features in DM.

Identification of a CCDC114 variant in a Han-Chinese patient with situs inversus

The function and position of the internal organs within the human body are based on left-right (LR) asymmetry. Human LR asymmetry disorders are characterized by abnormal LR asymmetric arrangement of the internal organs resulting from defective embryonic nodal cilia and nodal signaling pathway. The coiled-coil domain containing 114 gene (CCDC114) is related to the biogenesis of cilia and attachment of the outer dynein arms (ODAs) to the axoneme of cilia. Mutations in the CCDC114 gene are reported to cause a subtype of primary ciliary dyskinesia (PCD) named ciliary dyskinesia, primary, 20 (CILD20). Patients with CCDC114 mutations present with a type of ciliopathy with high clinical heterogeneity. In the present study, a Han-Chinese patient with situs inversus was recruited. Exome sequencing was performed on this patient combined with variant validation by Sanger sequencing. A homozygous variant c.584T>C (p.L195P) in the CCDC114 gene was identified as the likely genetic cause for situs inversus in this patient. The findings of our study extend the mutational spectrum of the CCDC114 gene, and contribute to clarifying the pathogenesis of human ciliopathies and benefit genetic counseling.

A case of Usher syndrome type IIA caused by a rare USH2A homozygous frameshift variant with maternal uniparental disomy (UPD) in a Chinese family

Usher syndrome encompasses a group of genetically and clinically heterogeneous autosomal recessive disorders with hearing deficiencies and retinitis pigmentosa. The mechanisms underlying the Usher syndrome are highly variable. In the present study, a Chinese family with Usher syndrome was recruited. Whole exome sequencing (WES), Sanger sequencing, homozygosity mapping, short tandem repeat (STR) analysis and segregation analysis were performed. Functional domains of the pathogenic variant for USH2A were analysed. We identified a homozygous frameshift variant c.99_100insT (p.Arg34Serfs*41) in the USH2A gene in the proband that showed discordant segregation in the father. Further homozygosity mapping and STR analysis identified an unusual homozygous variant of proband that originated from maternal uniparental disomy (UPD). The p.Arg34Serfs*41 variant produced a predicted truncated protein that removes all functional domains of USH2A. The variant was not included in the 1000 Human Genomes Project database, ExAC database, HGMD or gnomAD database, but was included in the ClinVar databases as pathogenic. Although USH2A is an autosomal recessive disease, the effects of UPD should be informed in genetic counselling since the recurrence risk of an affected child is greatly reduced when the disease is due to the UPD mechanism. To test potential patients, WES, combined with STR analysis and homozygosity mapping, provides an accurate and useful strategy for genetic diagnosis. In summary, our discoveries can help further the understanding of the molecular pathogenesis of Usher syndrome type IIA to advance the prevention, diagnosis and therapy for this disorder.

Monitoring and Management of the Patient with Stargardt Disease

Stargardt disease (STGD1) represents one of the major common causes of inherited irreversible visual loss. Due to its high phenotypic and genotypic heterogeneity, STGD1 is a complex disease to understand. Non-invasive imaging, biochemical, and genetic advances have led to substantial improvements in unveiling the disease processes and novel promising therapeutic landscapes have been proposed. This review recapitulates the modalities for monitoring patients with STGD1 and the therapeutic options currently under investigation for the different stages of the disease.