Recessive Mode Research Articles

Study of single nucleotide polymorphisms and serum level of E-cadherin and their relation to psoriasis severity

Backgroundpsoriasis is a persistent autoimmune-mediated systemic inflammatory illness that affects the skin and several organ systems. A family of calcium-dependent cell adhesion molecules called cadherins (CDH) works through homophilic contacts to keep cells attached to one another. In comparison to normal skin, several investigations found that the expression of E-cadherin was downregulated in the granular and basal layers of psoriasis lesional skin. ObjectivesThis study aimed to relate the serum level of E-cadherin and its genes (rs17715799 and rs13689) SNPs with the severity of psoriasis. MethodsIn the current study, 120 participants were divided into two groups: 60 patients with plaque psoriasis were in group I, and 60 healthy controls were in group II. The serum level of E-cadherin protein was measured using an enzyme linked immunosorbent assay (ELISA), and SNPs in the E-cadherin gene (rs17715799 and rs13689) were identified using real-time polymerase chain reaction (RT-PCR) technology. ResultsIn our study group I had a considerably higher serum level of the protein E-cadherin. It was confirmed that the E cadherin (rs13689) genotype frequency distribution revealed a significant difference between the two studied groups. The frequency of the CC genotype was higher in group I. While there was no significant variation in the genotype frequency distribution of E-cadherin (rs17715799) between the two study groups under the dominant, over-dominant, and recessive modes of inheritance (p 0.204) conclusion: patients with psoriasis had considerably higher serum levels of E-cadherin. The E-cadherin gene rs13689 polymorphism affects the chance of developing psoriasis. However, the E-cadherin gene rs17715799 polymorphism has no impact on the onset of psoriasis. As a result, the E-cadherin gene rs13689 but not rs17715799 might be considered as a marker for the risk of developing psoriasis.

Osteopetrosis associated with PLEKHM1 and SNX10 genes, both involved in osteoclast vesicular trafficking.

The clinical and radiological variability seen in different forms of osteopetrosis, all due to impaired osteoclastic bone resorption, reflect many causal genes. Both defective differentiation of osteoclasts from hematopoietic stem cells as well as disturbed functioning of osteoclasts can be the underlying pathogenic mechanism. Pathogenic variants in PLEKHM1 and SNX10 can be classified among the latter as they impair vesicular transport within the osteoclast and therefore result in the absence of a ruffled border. Some of the typical radiological hallmarks of osteopetrosis can be seen, and most cases present as a relatively mild form segregating in an autosomal recessive mode of inheritance.

Whole-exome sequencing identified a homozygous novel RAG1 mutation in a child with omenn syndrome.

Omenn syndrome (OS) is a very rare type of severe combined immunodeficiencies manifested with erythroderma, eosinophilia, hepatosplenomegaly, lymph-adenopathy, and elevated level of serum IgE. OS is inherited with an autosomal recessive mode of inheritance. Germline mutations in the human RAG1 gene cause OS. In this study, we investigated a 2-month-old boy with cough, mild anaemia, pneumonia, immunodeficiency, repeated infection, feeding difficulties, hepatomegaly, growth retardation, and heart failure. Parents of the proband were phenotypically normal. Karyotype analysis and chromosomal microarray analysis found no chromosomal structural abnormalities (46, XY) and no pathogenic copy number variations (CNVs) in the proband. Whole-exome sequencing identified a novel homozygous single nucleotide deletion (c.2662delC) in exon 2 of the RAG1 gene in the proband. Sanger sequencing confirmed that both the proband parents were carrying this variant in a heterozygous state. This variant was not identified in two elder sisters and one elder brother of the proband and in the 100 ethnically matched normal healthy individuals. This novel homozygous deletion (c.2662delC) leads to the frameshift, which finally results in the formation of the truncated protein (p.Leu888Phefs*3) V(D)J recombination-activating protein 1 with 890 amino acids compared with the wildtype V(D)J recombination-activating protein 1 of 1043 amino acids. Hence, it is a loss-of-function variant. Our present study expands the mutational spectrum of the RAG1 gene associated with OS. We also strongly suggested the importance of whole-exome sequencing for the genetic screening of patients with OS.

Mutation of the MYH3 gene causes recessive cleft palate in Limousine cattle

BackgroundThe palate is a structure separating the oral and nasal cavities and its integrity is essential for feeding and breathing. The total or partial opening of the palate is called a cleft palate and is a common malformation in mammals with environmental or hereditary aetiologies. Generally, it compromises life expectancy in the absence of surgical repair. A new form of non-syndromic cleft palate arose recently in Limousine cattle, with animals referred to the French National Observatory of Bovine Abnormalities since 2012. Since the number of affected animals has increased steadily, this study was undertaken to identify the cause of this disease.ResultsBased on pedigree analysis, occurrence of cleft palate in Limousine cattle was concordant with an autosomal recessive mode of inheritance. Genotyping of 16 affected animals and homozygosity mapping led to the identification of a single disease-associated haplotype on Bos taurus chromosome (BTA)19. The genome of two affected animals was sequenced, and their sequences were compared to the ARS-UCD1.2 reference genome to identify variants. The likely causal variants were compared to the variant database of the 1000 bull genome project and two fully linked mutations in exon 24 of the MYH3 (myosin heavy chain) gene were detected: a 1-bp non-synonymous substitution (BTA19:g.29609623A>G) and a 11-bp frameshift deletion (BTA19:g.29609605-29609615del). These two mutations were specific to the Limousine breed, with an estimated allele frequency of 2.4% and are predicted to be deleterious. The frameshift leads to a premature termination codon. Accordingly, mRNA and protein analyses in muscles from wild-type and affected animals revealed a decrease in MYH3 expression in affected animals, probably due to mRNA decay, as well as an absence of the MYH3 protein in these animals. MYH3 is mostly expressed in muscles, including craniofacial muscles, during embryogenesis, and its absence may impair palate formation.ConclusionsWe describe a new form of hereditary cleft palate in Limousine cattle. We identified two fully linked and deleterious mutations, ultimately leading to the loss-of-function of the MYH3 protein. The mutations were included on the Illumina EuroG10k v8 and EuroGMD v1 SNP chips and are used to set up a reliable eradication strategy in the French Limousine breed.

Association between neuropeptide Y gene polymorphism and antipsychotics effect.

The pathogenesis of schizophrenia is associated with neuropeptide Y (NPY) gene polymorphism to explore the relationship between rs16141, rs16145, and rs5573 polymorphisms in the NPY gene and antipsychotics response in the Chinese population. The unrelated 228 Chinese Han patients with schizophrenia were enrolled in the present study. Genotypisation within NPY gene was performed using the KASP genotyping assays. Before treatment and on the weekends of the 2nd, 4th, and 8th weeks after treatment, the medication status of the patients was recorded and the positive and negative syndrome scale (PANSS) was used to evaluate the clinical effect. A reduction in total PANSS scores ≥50% were classified as good responders, while others were poor responders. We evaluated the association between NPY gene and antipsychotic efficacy by comparing allele and genotype distribution, correlation analysis, linkage imbalance, and five genetic models between the two groups. No significant associations were found in the rs16141, rs16145, and rs5573 of NPY and antipsychotic treatment response (all p > 0.05). There was no significant relationship between the three SNPs polymorphisms in the NPY gene and the changes of positive, negative and general psychopathology subscales scores at each stage (all p > 0.05). The distribution of genotype and allele frequencies of locus rs16141 was not statistically difference between good responders and poor responders (genotype: χ2 =4.088, p=0.043, p-correction = 0.129; allele: χ2 = 4.088, p = 0.027, p-correction = 0.081). The allele distribution of rs5573 was significantly different between groups, yet the difference was disappeared after correcting (χ2 = 4.136, p = 0.042, p-correction =0.126). The distribution frequencies of TA/TG and GG haplotypes constituted by rs16141 and rs5573 showed no statistical difference between the two groups (p > 0.05). In recessive inheritance mode, NPYrs5573 was found to be associated with antipsychotic drug response (G/G vs. A/A +A/G: p = 0.028, AIC = 197.2, BIC = 210.9). This study didn't found association between polymorphisms in the NPY gene locus (rs16141, rs16145, and rs5573) and the response to antipsychotics after Bonferroni correction. The polymorphism of NPY gene and the efficacy of antipsychotic drugs in patients with schizophrenia need further study.

Genetic Characterisation of Pantothenate Kinase Associated Neurodegeneration (PKAN) in a Consanguineous Family from Jammu and Kashmir India

Pantothenate kinase-associated neurodegeneration (PKAN), a rare neurological disorder occurs by variation(s) in the PANK2 (Pantothenate kinase 2) gene and is linked to iron accumulation in the basal ganglia. The researchers have carried out targeted gene sequencing of all exons of PANK2 in a patient with suspected phenotype of PKAN. A missense variant in exon 6 of PANK2 gene (NM_153638.3:c.1583C>T,NP_705902.2:p.Thr528Met) has been identified in the patient. Further, sequencing of the exon in extended consanguineous family showed autosomal recessive mode of inheritance in the family. It is emphasised that inclusion of molecular diagnostics in clinical evaluation procedures of potential genetic or uncharacterised abnormalities is critical especially if the family has known history of high consanguinity. It is anticipated to provide effectively, such families with access to a variety of genetic counselling programmes, thus reducing illness burden in the affected family.

EHBP1L1 Frameshift Deletion in English Springer Spaniel Dogs with Dyserythropoietic Anemia and Myopathy Syndrome (DAMS) or Neonatal Losses.

Hereditary myopathies are well documented in dogs, whereas hereditary dyserythropoietic anemias are rarely seen. The aim of this study was to further characterize the clinical and clinicopathological features of and to identify the causative genetic variant for a dyserythropoietic anemia and myopathy syndrome (DAMS) in English springer spaniel dogs (ESSPs). Twenty-six ESSPs, including five dogs with DAMS and two puppies that died perinatally, were studied. Progressive weakness, muscle atrophy—particularly of the temporal and pelvic muscles—trismus, dysphagia, and regurgitation due to megaesophagus were observed at all ages. Affected dogs had a non-regenerative, microcytic hypochromic anemia with metarubricytosis, target cells, and acanthocytes. Marked erythroid hyperplasia and dyserythropoiesis with non-orderly maturation of erythrocytes and inappropriate microcytic metarubricytosis were present. Muscle biopsies showed centralized nuclei, central pallor, lipocyte infiltrates, and fibrosis, which was consistent with centronuclear myopathy. The genome sequencing of two affected dogs was compared to 782 genomes of different canine breeds. A homozygous frameshift single-base deletion in EHBP1L1 was identified; this gene was not previously associated with DAMS. Pedigree analysis confirmed that the affected ESSPs were related. Variant genotyping showed appropriate complete segregation in the family, which was consistent with an autosomal recessive mode of inheritance. This study expands the known genotype–phenotype correlation of EHBP1L1 and the list of potential causative genes in dyserythropoietic anemias and myopathies in humans. EHBP1L1 deficiency was previously reported as perinatally lethal in humans and knockout mice. Our findings enable the genetic testing of ESSP dogs for early diagnosis and disease prevention through targeted breeding strategies.

Allele-biased expression of the bovine APOB gene associated with the cholesterol deficiency defect suggests cis-regulatory enhancer effects of the LTR retrotransposon insertion

The insertion of an endogenous retroviral long terminal repeat (LTR) sequence into the bovine apolipoprotein B (APOB) gene is causal to the inherited genetic defect cholesterol deficiency (CD) observed in neonatal and young calves. Affected calves suffer from developmental abnormalities, symptoms of incurable diarrhoea and often die within weeks to a few months after birth. Neither the detailed effects of the LTR insertion on APOB expression profile nor the specific mode of inheritance nor detailed phenotypic consequences of the mutation are undisputed. In our study, we analysed German Holstein dairy heifers at the peak of hepatic metabolic load and exposed to an additional pathogen challenge for clinical, metabolic and hepatic transcriptome differences between wild type (CDF) and heterozygote carriers of the mutation (CDC). Our data revealed that a divergent allele-biased expression pattern of the APOB gene in heterozygous CDC animals leads to a tenfold higher expression of exons upstream and a decreased expression of exons downstream of the LTR insertion compared to expression levels of CDF animals. This expression pattern could be a result of enhancer activity induced by the LTR insertion, in addition to a previously reported artificial polyadenylation signal. Thus, our data support a regulatory potential of mobile element insertions. With regard to the phenotype generated by the LTR insertion, heterozygote CDC carriers display significantly differential hepatic expression of genes involved in cholesterol biosynthesis and lipid metabolism. Phenotypically, CDC carriers show a significantly affected lipomobilization compared to wild type animals. These results reject a completely recessive mode of inheritance for the CD defect, which should be considered for selection decisions in the affected population. Exemplarily, our results illustrate the regulatory impact of mobile element insertions not only on specific host target gene expression but also on global transcriptome profiles with subsequent biological, functional and phenotypic consequences in a natural in-vivo model of a non-model mammalian organism.

Investigation on Probable Association Between IL-13, IL-13RA1, and IL-13RA2 Genes Polymorphism and Pulmonary Tuberculosis.

ObjectiveOur study aimed to explore the association of IL-13, IL-13RA1, and IL-13RA2 genes polymorphisms with PTB susceptibility and its clinical features.MethodsNine SNPs were genotyped by improved multiple ligase detection reaction (iMLDR) in 476 PTB patients and 473 controls. The association between these SNPs and PTB risk was analyzed using SPSS software and haplotype analysis was assessed using SHEsis software.ResultsThe IL-13RA1 rs2495636 GA genotype frequency in PTB patients was significantly decreased, and IL-13RA2 rs5946039 A allele was related to the lower risk of PTB. In IL-13 gene, rs20541 variant was found to be associated with PTB risk under recessive mode. Moreover, IL-13RA1 rs141573089 C allele was significantly lower in PTB presenting with fever, drug resistance, and CC genotype was decreased in PTB presenting with leukopenia. IL-13RA1 rs2495636 polymorphism was associated with drug resistance, pulmonary infection, and IL-13RA2 rs3795175, rs638376 polymorphisms were related to drug resistance in PTB patients.ConclusionIL-13 rs20541, IL-13RA1 rs2495636, IL-13RA2 rs5946039 polymorphisms might be contributed to the genetic background of PTB in Chinese population.

Compound Heterozygous Variants of the CPAMD8 Gene Co-Segregating in Two Chinese Pedigrees With Pigment Dispersion Syndrome/Pigmentary Glaucoma.

The molecular mechanisms underlying the pathogenesis of pigment dispersion syndrome and pigmentary glaucoma remain unclear. In pedigree-based studies, familial aggregation and recurrences in relatives suggest a strong genetic basis for pigmentary glaucoma. In this study, we aimed to identify the genetic background of two Chinese pedigrees with pigmentary glaucoma. All members of these two pedigrees who enrolled in the study underwent a comprehensive ophthalmologic examination, and genomic DNA was extracted from peripheral venous blood samples. Whole-exome sequencing and candidate gene verifications were performed to identify the disease-causing variants; in addition, screening of the CPAMD8 gene was performed on 38 patients of sporadic pigmentary glaucoma. Changes in the structure and function of abnormal proteins caused by gene variants were analyzed with a bioinformatics assessment. Pigmentary glaucoma was identified in a total of five patients from the two pedigrees, as were compound heterozygous variants of the CPAMD8 gene. No signs of pigmentary glaucoma were found in carriers of monoallelic CPAMD8 variant/variants. All four variants were inherited in an autosomal recessive mode. In addition to the 38 patients of sporadic pigmentary glaucoma, 13 variants of the CPAMD8 gene were identified in 11 patients. This study reported a possible association between CPAMD8 variants and pigment dispersion syndrome/pigmentary glaucoma.

SLC25A12 Missense Variant in Nova Scotia Duck Tolling Retrievers Affected by Cerebellar Degeneration-Myositis Complex (CDMC).

We investigated two litters of distantly related Nova Scotia Duck Tolling Retrievers (NSDTR), of which four puppies were affected by cerebellar signs with or without neuromuscular weakness. The phenotype was termed cerebellar degeneration—myositis complex (CDMC). We suspected a heritable condition and initiated a genetic analysis. The genome of one affected dog was sequenced and compared to 565 control genomes. This search yielded a private protein-changing SLC25A12 variant in the affected dog, XM_038584842.1:c.1337C>T, predicted to result in the amino acid change XP_038440770.1:(p.Pro446Leu). The genotypes at the variant co-segregated with the phenotype as expected for a monogenic autosomal recessive mode of inheritance in both litters. Genotyping of 533 additional NSDTR revealed variant allele frequencies of 3.6% and 1.3% in a European and a North American cohort, respectively. The available clinical and biochemical data, together with current knowledge about SLC25A12 variants and their functional impact in humans, mice, and dogs, suggest the p.Pro446Leu variant is a candidate causative defect for the observed phenotype in the affected dogs.

P-559 Preimplantation genetic testing for monogenic diseases : are there any predictive factors for live birth rate ?

Abstract Study question Does the chance of having a healthy baby after PGT-M differ according to the known risk of inherited genetic pathology: autosomal recessive or dominant mode? Summary answer Live birth after PGT-M is not impacted by the inherited mode of genetic transmission. Age and ovarian reserve markers are predictive factors. What is known already The effectiveness of PGT-M, is conditioned by the number of healthy embryos obtained and therefore by a sufficient number of collected oocytes. Depending on the mode of genetic transmission, the probability of having a healthy embryo after cells biopsy varies from 25% (recessive transmission mode) to 50% (dominant transmission mode). It was commonly assumed that CLBR is directly impacted by female age but there are no published study related how the inherited transmission mode of the disease requiring PGT-M affects the chance to have a healthy baby. Study design, size, duration The present study is a monocentric retrospective observational study carried out from January 2006 through January 2020 in a French PGT center. Four hundred and seventy-four couples undergoing molecular PGT-M were classified into two groups based on risk of disease transmission (25% risk, P25 group or 50% risk, P50 group). Participants/materials, setting, methods Among the included patients, 267 patients were classified as “½ risk of transmission” and 207 patients were classified as “1/4 risk of transmission.” We compared the chances of having a healthy baby for these two groups and studied the predictive factors for obtaining a live birth. Main results and the role of chance Women's characteristics at the time of first ovarian stimulation were not significantly different between P25 group and P50 group. While the mean number of embryos biopsied per couple was not significantly different between groups (9.6±8.6 vs. 8.5±7.3, p = 0.3), the mean number of healthy embryos obtained after PGT-M was significantly higher for the P25 group compared to the P50 group (5.0±4.1 vs. 3.9±3.6, p = 0.001). However, the chances of having at least one heathly child after PGT-M were not significantly different according to the P25 or P50 group (41.5% vs. 35.9% respectively, p = 0.2). We found that women’s age, AMH and CFA were predictive factors ofhaving a healthy baby. Patients aged 31 years and younger had a 45% higher chance of having a live birth than women aged 32 to 35 years (p = 0.04). Patients with AMH≥4.5ng/ml or CFA ≥22 follicles were significantly more likely to have a live birth than women with AMH ≤2.27 ng/ml or CFA < 15 (OR = 1.58 (1.19-2.09) p = 0.001 and OR = 1.33 (1.01-1.75), p = 0.03 respectively). Limitations, reasons for caution This study is retrospective. Despite the large sample size, the findings are confined by limited coufounder adjustment and the lack of specific PGT-M comparators. Wider implications of the findings Age, AMH, and AFC are associated as good prognosis factors to have a live birth. The genetic mode of transmission ½ or ¼ was not found to be a predictive factor. This allows couples to make the best choice between PGT and other reproductive options (gamete donation, adoption). Trial registration number not applicable

Whole exome sequencing identified a homozygous novel mutation in SUOX gene causes extremely rare autosomal recessive isolated sulfite oxidase deficiency

BackgroundIsolated sulfite oxidase deficiency (ISOD) is a rare type of life-threatening neurometabolic disorders characterized by neonatal intractable seizures and severe developmental delay with an autosomal recessive mode of inheritance. Germline mutation in SUOX gene causes ISOD. Till date, only 32 mutations of SUOX gene have been identified and reported to be associated with ISOD. MethodsHere, we investigated a 5-days old Chinese female child, presented with intermittent tremor or seizures of limbs, neonatal encephalopathy, subarachnoid cyst and haemorrhage, dysplasia of corpus callosum, neonatal convulsion, hyperlactatemia, severe metabolic acidosis, hyperglycemia, and hyperkalemia. ResultsWhole exome sequencing identified a novel homozygous transition (c.1227G > A) in exon 6 of the SUOX gene in the proband. This novel homozygous variant leads to the formation of a truncated sulfite oxidase (p.Trp409*) of 408 amino acids. This variant causes partial loss of the dimerization domain of sulfite oxidase. Hence, it is a loss-of-function variant. Proband’s father and mother is carrying this novel variant in a heterozygous state. This variant was not found in 200 ethnically matched normal healthy control individuals. ConclusionsOur study not only expanded the mutational spectrum of SUOX gene associated with ISOD, but also strongly suggested the significance of whole exome sequencing for identifying candidate genes and novel disease-causing variants.

Exome Sequencing Identifies the Extremely Rare ITGAV and FN1 Variants in Early Onset Inflammatory Bowel Disease Patients.

BackgroundMolecular diagnosis of early onset inflammatory bowel disease (IBD) is very important for adopting suitable treatment strategies. Owing to the sparse data available, this study aims to identify the molecular basis of early onset IBD in Arab patients.MethodsA consanguineous Arab family with monozygotic twins presenting early onset IBD was screened by whole exome sequencing (WES). The variants functional characterization was performed by a series of computational biology methods. The IBD variants were further screened in in-house whole exome data of 100 Saudi cohorts ensure their rare prevalence in the population.ResultsGenetic screening has identified the digenic autosomal recessive mode of inheritance of ITGAV (G58V) and FN1 (G313V) variants in IBD twins with early onset IBD. Findings from pathogenicity predictions, stability and molecular dynamics have confirmed the deleterious nature of both variants on structural features of the corresponding proteins. Functional biology data suggested that both genes show abundant expression in gastrointestinal tract and immune organs, involved in immune cell restriction, regulation of different immune related pathways. Data from knockout mouse models for ITGAV gene has revealed that the dysregulated expression of this gene impacts intestinal immune homeostasis. The defective ITGAV and FN1 involved in integrin pathway, are likely to induce intestinal inflammation by disturbing immune homeostasis.ConclusionsOur findings provide novel insights into the molecular etiology of pediatric onset IBD and may likely pave way in developing genomic medicine.

Bi-allelic TTC21A mutations in common variable immunodeficiency patients

Abstract Very little is known about the gene TTC21A – it was first described as a gene in the AP20 sub-region of chr3p.21.3 in which deletions were associated with cancer. Initially, TTC21A mRNA expression was only found in the testis, consistent with a recent study linking homozygous TTC21A mutations to decreased fertility due to structural defects in sperm flagella. Interestingly, the gene is also expressed in B lymphocytes with several smaller predicted protein coding transcripts enriched particularly in naïve and memory B cells. Here we report four individuals of one kindred with common variable immunodeficiency (CVID) with two different sets of rare biallelic TTC21A variants. Based on whole genome sequencing analysis, TTC21A was the only candidate gene that co-segregated with disease across three generations and eight individuals of this family with an autosomal recessive mode of inheritance. The affected individuals had low serum IgG and a significant defect in class-switching. In-depth B cell immunophenotyping revealed that, relative to healthy family controls, the patients had significant skewing of increased transitional (CD27− IgD+ CD24+ CD38+) B cells and markedly reduced terminally differentiated plasmablasts (IgD− CD20low CD38+). The patients with the rare homozygous variant also had significantly reduced expression of the B cell specific TT21A variant relative to the family controls and patients with the compound heterozygous variants. Initial immunization experiments of Ttc21a CRISPR knock-in mice mirrored the patients’ phenotype with decreased class switching; however subsequent repeats have been inconclusive. Additional work is necessary to further elucidate the immune function of TTC21A in B cells. Supported by the NIH Oxford-Cambridge MD/PhD Scholarship

P514. Excess of Homozygous Ultra-Rare Exonic Variants in Schizophrenia: Evidence for Recessive Effects

To date, rare variant research in schizophrenia (SZ) has focused on dominant exonic variants; there has been limited research examining the recessive mode of inheritance. The Ashkenazi Jewish (AJ) population is marked by an excess of homozygosity, due to a history of endogamy and a small founder population, and may provide enhanced power for studies of recessive loci.

Exome sequencing of families from Ghana reveals known and candidate hearing impairment genes

We investigated hearing impairment (HI) in 51 families from Ghana with at least two affected members that were negative for GJB2 pathogenic variants. DNA samples from 184 family members underwent whole-exome sequencing (WES). Variants were found in 14 known non-syndromic HI (NSHI) genes [26/51 (51.0%) families], five genes that can underlie either syndromic HI or NSHI [13/51 (25.5%)], and one syndromic HI gene [1/51 (2.0%)]. Variants in CDH23 and MYO15A contributed the most to HI [31.4% (16/51 families)]. For DSPP, an autosomal recessive mode of inheritance was detected. Post-lingual expression was observed for a family segregating a MARVELD2 variant. To our knowledge, seven novel candidate HI genes were identified (13.7%), with six associated with NSHI (INPP4B, CCDC141, MYO19, DNAH11, POTEI, and SOX9); and one (PAX8) with Waardenburg syndrome. MYO19 and DNAH11 were replicated in unrelated Ghanaian probands. Six of the novel genes were expressed in mouse inner ear. It is known that Pax8-/- mice do not respond to sound, and depletion of Sox9 resulted in defective vestibular structures and abnormal utricle development. Most variants (48/60; 80.0%) have not previously been associated with HI. Identifying seven candidate genes in this study emphasizes the potential of novel HI genes discovery in Africa.

Early onset adult deafness in the Rhodesian Ridgeback dog is associated with an in-frame deletion in the EPS8L2 gene.

Domestic dogs exhibit diverse types of both congenital and non-congenital hearing losses. Rhodesian Ridgebacks can suffer from a progressive hearing loss in the early stage of their life, a condition known as early onset adult deafness (EOAD), where they lose their hearing ability within 1-2 years after birth. In order to investigate the genetic basis of this hereditary hearing disorder, we performed a genome-wide association study (GWAS) by using a sample of 23 affected and 162 control Rhodesian Ridgebacks. We identified a genomic region on canine chromosome 18 (CFA18) that is strongly associated with EOAD, and our subsequent targeted Sanger sequencing analysis identified a 12-bp inframe deletion in EPS8L2 (CFA18:25,868,739-25,868,751 in the UMICH_Zoey_3.1/canFam5 reference genome build). Additional genotyping confirmed a strong association between the 12-bp deletion and EOAD, where all affected dogs were homozygous for the deletion, while none of the control dogs was a deletion homozygote. A segregation pattern of this deletion in a 2-generation nuclear family indicated an autosomal recessive mode of inheritance. Since EPS8L2 plays a critical role in the maintenance and integrity of the inner ear hair cells in humans and other mammals, the inframe deletion found in this study represents a strong candidate causal mutation for EOAD in Rhodesian Ridgebacks. Genetic and clinical similarities between childhood deafness in humans and EOAD in Rhodesian Ridgebacks emphasizes the potential value of this dog breed in translational research in hereditary hearing disorders.

Xeroderma Pigmentosum-Associated Childhood Interstitial Lung Disease.

Chromosomal breakage syndromes are a group of genetic disorders that are ascribable to the autosomal recessive mode of inheritance. Xeroderma pigmentosum is one of the chromosomal breakage syndromes which is due to the involvement of deformity in the deoxyribonucleic acid’s nucleotide excision repair. Xeroderma pigmentosum is a genetic disorder, which is autosomal recessive, heterogeneous, and more common in cases of consanguinity, caused by mutations in at least 10 genes and 9 complementation groups. The disorder is very rare. Patients experience photophobia and extreme photosensitivity and have pigmentary changes in ultraviolet light-exposed areas of the body with freckling, premalignant, and malignant skin lesions arising in keratinocytes soon after the fleeting exposure to sunlight. Patients are also oversensitive to environmental mutagens such as cigarette smoke and possibly to the widely used agricultural insecticide, diazinon. Progressive neurological abnormalities along with some rare complications are also noticed among these patients. Symptoms and thoracic high-resolution computed tomography are considered for diagnosis. Only corticosteroids can be given to limit the progression of the disease. Xeroderma pigmentosum-related interstitial lung disease is one of the rarest forms and we thereby report an interesting case.

Wolfram Syndrome 1: From Genetics to Therapy.

Wolfram syndrome 1 (WS1) is a rare neurodegenerative disease transmitted in an autosomal recessive mode. It is characterized by diabetes insipidus (DI), diabetes mellitus (DM), optic atrophy (OA), and sensorineural hearing loss (D) (DIDMOAD). The clinical picture may be complicated by other symptoms, such as urinary tract, endocrinological, psychiatric, and neurological abnormalities. WS1 is caused by mutations in the WFS1 gene located on chromosome 4p16 that encodes a transmembrane protein named wolframin. Many studies have shown that wolframin regulates some mechanisms of ER calcium homeostasis and therefore plays a role in cellular apoptosis. More than 200 mutations are responsible for WS1. However, abnormal phenotypes of WS with or without DM, inherited in an autosomal dominant mode and associated with one or more WFS1 mutations, have been found. Furthermore, recessive Wolfram-like disease without DM has been described. The prognosis of WS1 is poor, and the death occurs prematurely. Although there are no therapies that can slow or stop WS1, a careful clinical monitoring can help patients during the rapid progression of the disease, thus improving their quality of life. In this review, we describe natural history and etiology of WS1 and suggest criteria for a most pertinent approach to the diagnosis and clinical follow up. We also describe the hallmarks of new therapies for WS1.