Genotypic spectrum of ABCA4-associated retinal degenerations in 211 unrelated Mexican patients: identification of 22 novel disease-causing variants.

The purpose of this study was to analyze and molecularly describe the largest group of patients with ABCA4-associated retinal degeneration in Latin America. Pathogenic variants in ABCA4, a member of the ATP Binding Cassette (ABC) transporters superfamily, is one of the most common causes of inherited visual deficiency in humans. Retinal phenotypes associated with genetic defects in ABCA4 are collectively known as ABCA4-associated retinal degenerations (ABCA4R), a group of recessively inherited disorders associated with a high allelic heterogeneity. While large groups of Caucasian and Asiatic individuals suffering from ABCA4R have been well characterized, molecular information from certain ethnic groups is limited or unavailable, precluding a more realistic knowledge of ABCA4-related mutational profile worldwide. In this study, we describe the molecular findings of a large group of 211 ABCA4R index cases from Mexico. Genotyping was performed using either next generation sequencing (NGS) of a retinal dystrophy genes panel or exome. ABCA4 targeted mutation testing was applied to a subgroup of subjects in whom founder mutations were suspected. A total of 128 different ABCA4 pathogenic variants were identified, including 22 previously unpublished variants. The most common type of genetic variation was single nucleotide substitutions which occurred in 92.7% (408/440 alleles). According to the predicted protein effect, the most frequent variant type was missense, occurring in 83.5% of disease-causing alleles (368/440). Mutations such as p.Ala1773Val are fully demonstrated as a founder effect in native inhabitants of certain regions of Mexico. This study also gives us certain indications of other founder effects that need to be further studied in the near future. This is the largest molecularly characterized ABCA4R Latin American cohort, and our results supports the value of conducting genetic screening in underrepresented populations for a better knowledge of the mutational profile leading to monogenic diseases.

TEK gene-related primary congenital glaucoma: Phenotypic features and mutational spectrum in a Mexican cohort of 10 unrelated families.

Primary congenital glaucoma (PCG) is one of the leading causes of visual damage and blindness, severely affecting the quality of life of affected children. It is characterized by cupping of the optic disc and loss of ganglion cells due to elevated intraocular pressure. While most PCG patients exhibit epiphora, photophobia, and buphthalmos with corneal opacity, variability in phenotypic manifestations is not uncommon. Prompt diagnosis and treatment of PCG affected individuals becomes relevant to preserve visual function throughout their lives. Most PCG cases are sporadic or autosomal recessive; however, an incompletely dominant autosomal dominant form arising from mutations in the TEK gene has recently been demonstrated. Here, we describe the clinical and mutational features of a cohort of Mexican patients with TEK-related PCG. Our results support the involvement of the TEK gene as an important cause of the disease in our ethnic group and expand the mutational spectrum causing PCG by reporting 10 novel disease-causing variants.

A novel homozygous ZNF469 variant causing brittle cornea syndrome is associated with corneal ectasias in heterozygous carriers.

AIM: To describe a family segregating a novel truncating ZNF469 homozygous mutation causing brittle cornea syndrome type 1 in a male patient and associated with corneal ectasia in his two heterozygous young children. METHODS: A 49-year-old affected male and his 12- and 8-year-old, apparently healthy, siblings underwent phenotypic and genetic assessment. An Oculus Pentacam Scheimpflug topographer system was employed for keratometries and central corneal thickness measurements. Exome sequencing was performed in DNA from the index case with subsequent Sanger sequencing confirmation of the ZNF469 gene causal variant in his relatives. RESULTS: The index case had a history of bilateral keratoglobus, corneal perforations, bilateral hypoacusia, and skeletal anomalies. His two children exhibited topographic anomalies compatible with keratoconus suspects as well as mild skeletal anomalies. Genetic analysis identified a novel homozygous c.2340delC variant in the ZNF469 gene, which predicts a p.(Arg781Glufs*19) truncated protein. Sanger sequencing identified heterozygosity for the c.2340delC variant in DNA from both siblings. CONCLUSION: Our results expand the mutational spectrum associated with brittle cornea syndrome and provide the first demonstration of early corneal anomalies in subjects carrying monoallelic ZNF469 variants.

Ophthalmic findings in patients with autosomal recessive lamellar ichthyosis due to TGM1 mutations in an isolated population.

PURPOSE: To describe the ocular clinical characteristics of a group of Mexican patients with lamellar ichthyosis (LI) arising from TGM1 pathogenic variants. METHODS: Ophthalmological exploration, pedigree analysis and genetic screening were performed in patients with an established clinical diagnosis of lamellar ichthyosis from families located in a small community in the Southeast of Mexico. RESULTS: Nine patients with LI in five families were identified. There were six affected females. All patients (9/9) demonstrated eye lid abnormalities with eight patients showing lid margin abnormalities. Madarosis was present in only three individuals and corneal scarring was documented in two. All nine individuals carried biallelic TGM1 variants, either homozygously or as compound heterozygous. CONCLUSION: Ocular anomalies are common in individuals with TGM1-related LI. The occurrence of a variety of private or rare mutations hampers the identification of a genotype-phenotype correlation for ocular anomalies in this disorder.

Clinical and Molecular Findings of Intermediate Allele Carriers in the HTT Gene from the Mexican Mestizo Population.

INTRODUCTION: There are reports of different clinical statuses in carriers of intermediate alleles (IAs) of CAG trinucleotide repeats in the HTT gene, from individuals affected by a clinical picture indistinguishable from Huntington's disease (HD) to those without manifestations. Therefore, the possible clinical significance of these alleles has been widely debated. OBJECTIVES: The aim of this study was to describe general and clinical features and discard HD phenocopies by molecular assessment in a case series of IA carriers on the HTT gene of a laboratory sample from a neurological center in Mexico. METHODS: We selected individuals who had previously been tested for the HTT gene expansion, which resulted in IAs. Clinical information was obtained from medical records, and molecular analysis of the JPH3, PRNP, and TBP genes was performed only in IA carriers with clinical manifestations. In addition, two patients with IA and acanthocytes were evaluated by whole-exome sequencing. The scientific and ethical committees of the National Institute of Neurology and Neurosurgery Manuel Velasco Suárez (NINNMVS) approved this study. RESULTS: From 1994 to 2019, the Genetics Department of the NINNMVS confirmed 34 individuals with IAs, 15 of whom belonged to 11 families with HD (IA-HD) and 19 of whom had no family history of HD (IA-non-HD). We found a high proportion of manifestations of the HD phenotypic spectrum in the IA-non-HD subgroup. In addition, among the 20 samples of IA carriers with manifestations molecularly evaluated, we identified two unrelated subjects with CAG/CTG repeat expansions on the JPH3 gene, confirming HD-like 2 (HDL2), and one patient with the homozygous pathogenic c.3232G>T variant (p.Glu1078Ter) in the VPS13A gene, demonstrating choreoacanthocytosis. DISCUSSION/CONCLUSION: Our results show the most extensive series of subjects with IAs and clinical manifestations. In addition, we identify three HD phenocopies, two HDL2 cases, and one choreoacanthocytosis case. Therefore, we emphasize evaluating other HD phenocopies in IA carriers with clinical manifestations whose family background is not associated with HD.

Exome sequencing identifies a SREBF1 recurrent ARG557CYS mutation as the cause of hereditary mucoepithelial dysplasia in a family with high clinical variability.

Hereditary mucoepithelial dysplasia (HMD) is an uncommon autosomal dominant disease affecting skin, mucosae, hair, eyes, and lungs. Prominent clinical features include non-scarring alopecia, mucosal erythema, perineal erythematous intertrigo, and involvement of the conjunctival mucosa. To date, 20 familial or sporadic HMD cases have been described, most of them originating from Caucasian ethnic groups. In this study, a novel HMD pedigree, including an affected father and his daughter, is reported. Clinical expression showed significant differences in affected subjects, especially in the distribution and severity of skin lesions. Exome sequencing demonstrated that both affected subjects carried a heterozygous c.1669C>T (p.Arg557Cys) pathogenic variant in the SREBF1 gene. Our results improve the knowledge of the clinical and genetic features of HMD. In addition, a comparative review of the clinical features of all published HMD cases is presented.

Differential Expression of the apsXRS System by Antimicrobial Peptide LL-37 in Commensal and Clinical Staphylococcus epidermidis Isolates.

The three-component apsXRS system senses and responds to cationic antimicrobial peptides (CAMPs), which induces the expression of the dlt operon and the genes mprF and vrafG, modifying the surface net charge in Staphylococcus epidermidis, resulting in the repulsion of CAMPs. The apsXRS system has been only studied in the S. epidermidis 1457 strain, and there are no studies of prevalence and level of expression of apsXRS in commensal and clinical isolates. From 60 isolates, those selected from commensal healthy skin (n = 20), commensal healthy conjunctive (n = 10), and clinical ocular infection (n = 30) presented the apsX, apsR, and apsS genes in their genomes. Constitutive expression of apsX, apsR, and apsS genes was determined by RT-qPCR in all isolates. It was found that expression of apsX, apsR, and apsS was 3.3-5.9-fold higher in commensal isolates stimulated with LL-37 (15 µg/mL) than in clinical isolates. Similarly, expression of the dlt operon and the genes mprF, and vraFG was 8-10-fold higher in commensal isolates than in clinical. However, LL-37 did not increase the addition of lysine in the phospholipids of the cytoplasmic membrane in any of the isolates. Mutations in the apsS loop region, apsR, and their promoter sequence were not found. These results demonstrated that apsXRS system is essential in all isolates for its constitutive expression; however, LL-37 caused an increase of apsXRS expression in commensal isolates, suggesting that S. epidermidis isolates do not respond in the same way to the presence of LL-37.

Duplication of SOX9 associated with 46,XX ovotesticular disorder of sex development.

RESEARCH QUESTION: The purpose of the present study was to investigate whether ten unrelated SRY-negative individuals with this sex differentiation disorder presented a double dose of SOX9 as the cause of their disease. DESIGN: Ten unrelated SRY-negative 46,XX ovotesticular disorder of sexual development (DSD) subjects were molecularly studied. Multiplex-ligation dependent probe amplification (MLPA) and quantitative real-time PCR analysis (qRT-PCR) for SOX9 were performed. RESULTS: The MLPA analysis demonstrated that one patient presented a heterozygous duplication of the entire SOX9 coding region (above 1.3 value of peak ratio), as well as at least a ~ 483 kb upstream duplication. Moreover, no duplication of other SOX9 probes was observed corresponding to the region between -1007 and -1500 kb upstream. A qRT-PCR analysis showed a duplication of at least -581 kb upstream and ~1.63 kb of the coding region that encompasses exon 3. The limits of the duplication were mapped approximately from ~71539762 to 72122741 of Chr17. No molecular abnormalities were found in the remaining nine patients. CONCLUSION: This study is thought to be the first report regarding a duplication of SOX9 that is associated with the presence of 46,XX ovotesticular DSD, encompassing at least -581 kb upstream, and the almost entire coding region of the gene.

PAX6 allelic heterogeneity in Mexican congenital aniridia patients: expanding the mutational spectrum with seven novel pathogenic variants.

IMPORTANCE: The importance of the study was to describe the clinical characteristics and mutational analysis of Mexican patients with aniridia. BACKGROUND: Aniridia is a panocular hereditary eye disease caused by mutations in the PAX6 transcription factor. Mutation detection rate is highly variable ranging from 30% to 90% in different populations. Very few studies have been published about the PAX6 mutational analysis in aniridia patients from Mexico. In order to establish a more representative PAX6 mutational frequency in the country, a cohort of 22 Mexican unrelated aniridia probands were analysed in this study. DESIGN: Case series. PARTICIPANTS: A total of 22 Mexican probands with bilateral isolated aniridia and their available relatives were included. METHODS: Sanger sequencing was used for the mutational analysis of all coding exons and flanking intronic regions of PAX6. MAIN OUTCOME MEASURES: Clinical characteristics and results of PAX6 mutational analysis in probands with aniridia and available family members. RESULTS: Molecular analysis of PAX6 in 22 index cases with aniridia allowed the identification of a total of 16 different mutations. Seven of these pathogenic variants are novel, including c.183C>G, p.(Y61*); c.718delC, p.(R240Efs*3); c.1149_1152delTCAG, p.(P385Wfs*139); c.257_266delAAATAGCCCA, p.(K86Sfs*35); c.836_843dupGCAACACA p.(P282Afs*86); c.1032+2_1032+3insT; and c.141+2T>A. Inter and intrafamilial phenotypic heterogeneity was found. CONCLUSIONS AND RELEVANCE: The mutational diagnostic rate in this series was 77%, which is comparable with reports from other populations. Importantly, no founder mutations were identified in this case series. Our results add 7 novel PAX6 pathogenic variants to the aniridia-related mutational spectrum and reveal considerable PAX6 allelic heterogeneity in this population.

[Gene therapy for vision restoration in patients with Leber congenital amaurosis (LCA) due to RPE65 gene mutations: beginning the phase IV trial]. / Terapia génica para la restauración de la visión en pacientes con amaurosis congénita de Leber (LCA) por mutación en el gen RPE65: el inicio de la fase IV.

This is a significant time moment in the field of gene therapy in humans. Recently, results from a phase III clinical trial were published, demonstrating the first gene therapy success for a genetic disease. A clinical trial was carried out in patients suffering a hereditary blindness disease named Leber congenital amaurosis, caused by mutations in the RPE65 gene. Participating subjects received a subretinal injection of the normal RPE65 gene and one year after exhibited a significant improvement in visual acuity. It is expected that this gene therapy treatment will be approved by the FDA and commercialized in the USA in 2017.

Genes relacionados con microftalmia y anoftalmia hereditarias.

Congenital eye malformations are the second most common cause of childhood blindness and are originated by disruption of the normal process of eye development during embryonic stage. Their etiology is variable, although monogenic causes are of great importance as they have a high risk of familial recurrence. Included among the most severe congenital eye abnormalities are microphthalmia, defined by an abnormally small eye, and anophthalmia, characterized by congenital absence of ocular structures. The currrent knowledge of the genes involved in human microphthalmia and anophthalmia in humans is revised in this work.

Tietz/Waardenburg type 2A syndrome associated with posterior microphthalmos in two unrelated patients with novel MITF gene mutations.

Tietz syndrome and Waardenburg syndrome type 2A are allelic conditions caused by MITF mutations. Tietz syndrome is inherited in an autosomal dominant pattern and is characterized by congenital deafness and generalized skin, hair, and eye hypopigmentation, while Waardenburg syndrome type 2A typically includes variable degrees of sensorineural hearing loss and patches of de-pigmented skin, hair, and irides. In this paper, we report two unrelated families with MITF mutations. The first family showed an autosomal dominant pattern and variable expressivity. The second patient was isolated. MITF gene analysis in the first family demonstrated a c.648A>C heterozygous mutation in exon 8 c.648A>C; p. (R216S), while in the isolated patient, an apparently de novo heterozygous c.1183_1184insG truncating mutation was demonstrated in exon 10. All patients except one had bilateral reduced ocular anteroposterior axial length and a high hyperopic refractive error corresponding to posterior microphthalmos, features that have not been described as part of the disease. Our results suggest that posterior microphthalmos might be part of the clinical characteristics of Tietz/Waardenburg syndrome type 2A and expand both the clinical and molecular spectrum of the disease. © 2016 Wiley Periodicals, Inc.

Clinical and Genetic Findings in Mexican Patients with Duane Anomaly and Radial Ray Malformations/Okihiro Syndrome.

BACKGROUND: Okihiro syndrome is an autosomal-dominant condition characterized by radial ray malformations associated with Duane anomaly and other clinical characteristics. SALL4 mutations have been identified in 80-90% of patients with Duane- Radial ray defects/Okihiro syndrome. We report the clinical findings and results of SALL4 sequencing from a group of Mexican patients with this disorder. OBJECTIVE: Clinical description and identification of SALL4 mutations in Mexican subjects with radial defects and Duane anomaly. MATERIALS AND METHODS: Five unrelated index cases were studied. Complete ophthalmologic and general physical examination was performed in all patients. Polymerase chain reaction amplification and automated nucleotide sequencing of coding exons and intron-exon junctions of SALL4 gene were carried out in genomic DNA. RESULTS: A novel heterozygous deletion was identified in one patient. Intragenic heterozygous single nucleotide polymorphisms on SALL4 gene ruled out deletions of some exons in other affected patients in whom non-pathogenic variants were identified by Sanger sequencing. Likewise, multiplex ligation-dependent probe amplification analysis ruled out large deletions in this gene. CONCLUSION: We observed a low frequency of SALL4 mutations in Mexican patients with clinical criteria of Okihiro syndrome.

SOX2 anophthalmia syndrome and dental anomalies.

SOX2 anophthalmia syndrome is an uncommon autosomal dominant syndrome caused by mutations in the SOX2 gene and clinically characterized by severe eye malformations (anophthalmia/microphthalmia) and extraocular anomalies mainly involving brain, esophagus, and genitalia. In this work, a patient with the SOX2 anophthalmia syndrome and exhibiting a novel dental anomaly is described. SOX2 genotyping in this patient revealed an apparently de novo c.70del20 deletion, a commonly reported SOX2 mutation. A review of the phenotypic variation observed in patients carrying the recurrent SOX2 c.70del20 mutation is presented. Although dental anomalies are uncommonly reported in the SOX2 anophthalmia syndrome, we suggest that a dental examination should be performed in patients with SOX2 mutations.

Acro-spondylo-pubic dysostosis associated with cataracts, microcephaly, and normal intelligence.

We report on an adult male with normal intelligence who exhibited an unusual combination of microcephaly, dysostoses of limbs, vertebrae, patellae, and pubic bone, camptodactyly of all fingers, and syndactyly of toes, absent nails on thumbs and some fingers, bilateral cataract, cryptorchidism, polythelia, and nipple-like skin pigmentations of shoulders and upper back. We have been unable to find a description of a similar combination of manifestations in literature. The cause of the anomalies remains unknown.

Triallelic digenic mutation in the prokineticin 2 and GNRH receptor genes in two brothers with normosmic congenital hypogonadotropic hypogonadism.

UNLABELLED: Purpose/aim of the study: To date, different genes have been identified as responsible for the presence of normosmic congenital hypogonadotropic hypogonadism (nCHH). Herein, we report the molecular findings regarding the analysis of PROK2, in two brothers with nCHH. SUBJECTS AND METHODS: Two siblings with nCHH, in whom mutations in GNRHR, PROKR2 and FGFR1 had been investigated previously, as well as their family were studied. DNA was amplified by PCR and sequenced for the PROK2 gene. Controls were analyzed by restriction fragment-length polymorphism. The structure of PROK2 and its mutant protein were compared using a protein molecular model. RESULTS: Both affected siblings exhibited a heterozygous p.R117W mutation in PROK2, while their mother was a heterozygous carrier and their father, an unaffected brother and their sister were homozygous wild type. Besides, both patients presented a homozygous p.E90K mutation in GNRHR that had been previously reported. CONCLUSIONS: We found a novel mutation in PROK2 in two siblings in whom a mutation in the GNRHR gene had been previously reported.

[Gene therapy for hereditary ophthalmological diseases: Advances and future perspectives]. / Terapia génica para enfermedades hereditarias oftalmológicas: avances y perspectivas.

Gene therapy is a promising new therapeutic strategy that could provide a novel and more effective way of targeting hereditary ophthalmological diseases. The eye is easily accessible, highly compartmentalized, and an immune-privileged organ that gives advantages as an ideal gene therapy target. Recently, important advances in the availability of various intraocular vector delivery routes and viral vectors that are able to efficiently transduce specific ocular cell types have been described. Gene therapy has advanced in some retinal inherited dystrophies; in this way, preliminary success is now being reported for the treatment of Leber congenital amaurosis (LCA). This review will provide an update in the field of gene therapy for the treatment of ocular inherited diseases.

CFH haplotypes and ARMS2, C2, C3, and CFB alleles show association with susceptibility to age-related macular degeneration in Mexicans.

PURPOSE: To evaluate the contribution of genetic variants of complement factor H (CFH), complement component 2 and 3 (C2 and C3), complement factor B (CFB), and age-related maculopathy susceptibility 2 (ARMS2) to age-related macular degeneration (AMD) risk in the Mexican Mestizo population. METHODS: Analysis included 282 unrelated Mexican patients with advanced AMD, 205 healthy controls, and 280 population controls. Stereoscopic fundus images were graded on the Clinical Age-Related Maculopathy System (CARMS). We designed a resequencing strategy using primers with M13 adaptor for the 23 exons of the CFH gene in a subgroup of 96 individuals clinically evaluated: 48 AMD cases and 48 age- and sex-matched healthy controls. Single nucleotide polymorphisms (SNPs) in C3 (Arg80Gly and Pro292Leu), C2 (rs547154), CFB (Leu9His), and ARMS2 (Ala69Ser) were genotyped in all patients, healthy and population controls using TaqMan assay. RESULTS: All evaluated individuals were Mexican Mestizos, and their genetic ancestry was validated using 224 ancestry informative markers and calculating F(st) values. The CFH resequencing revealed 19 SNPs and a common variant in the intron 2 splice acceptor site; three CFH haplotypes inferred from individual genotypes, showed significant differences between cases and controls. The risk alleles in C3 (rs1047286, odds ratio [OR]=2.48, 95% confidence interval [CI]=1.64-3.75, p=1.59E-05; rs2230199, OR=2.15, 95% CI=1.48-3.13, p=6.28E-05) and in ARMS2 (rs10490924, OR=3.09, 95% CI=2.48-3.86, p=5.42E-23) were strongly associated with risk of AMD. The protective effect of alleles in C2 (rs547154) and CFB (rs4151667) showed a trend but was not significantly associated after correction for multiple testing. CONCLUSIONS: Our results show that ARMS2 and C3 are major contributors to advanced AMD in Mexican patients, while the contributions of CFH, C2, and CFB are minor to those of other populations, reveling significant ethnic differences in minor allele frequencies. We provide evidence that two specific common haplotypes in the CFH gene predispose individuals to AMD, while another may confer reduced risk of disease in this admixed population.

[Prenatal exclusion of von Hippel-Lindau syndrome in a Mexican family carrying a novel VHL gene mutation]. / Exclusión prenatal del síndrome de von Hippel-Lindau en una familia Mexicana con una mutación nueva en el gen VHL.

BACKGROUND: von Hippel-Lindau (VHL) disease is an autosomal dominant and familial multisystemic syndrome that is caused by the inactivation of the VHL gene and it is characterized by diverse types of high vasculated tumours of benign and malign nature. In this work we describe the clinical characteristics and the prenatal diagnosis of a woman with VHL. OBJECTIVE: Describe the first exclusion prenatal case by DNA analysis of the VHL syndrome in Latinoamerican population. MATERIAL AND METHODS: Analysis of a Mexican familial pedigree showed 5 affected subjects with VHL on 3 consecutive generations. The proband was a 7 weeks pregnancy woman who was referred to our service for familiar and personal history of this disease. Maternal DNA was obtained from peripheral blood leukocytes, while fetal DNA was isolated from amniotic liquid cells on the 15th week. The maternal and fetal DNA analysis were done by the Polymerase Chain reaction (PCR) and the direct nucleotide sequence of the VHL gene. RESULTS: A novel mutation (c. 161_168 dup GGAGGCCG) in the VHL gene was identified in maternal DNA. Fetal DNA analysis indicated that the fetus inherited the wild-type allele from the mother. CONCLUSION: A novel VHL gene mutation was identified in a familial case of the disease, expanding the mutational spectrum in this disorder. The molecular prenatal testing in the affected woman at 15 weeks of gestation, demonstrated that the fetus did nor inherited the mutated allele. To the best of our knowledge, this is the first example of prenatal-molecular exclusion on VHL syndrome in Latinoamerica population.