Autosomal Recessive Mode Of Inheritance Research Articles

The identification of AMZ2 as a candidate causative gene in a severe teratozoospermia patient characterized by vacuolated spermatozoa.

Teratozoospermia with cephalic defects is one of the most severe types of sperm defects known to date. While several monogenic factors are linked to cephalic abnormalities, such as globozoospermia and macrozoospermia, the genetic cause of vacuolated spermatozoa remains inadequately described. Here, we analyzed whole-exome sequencing (WES) data for an individual from a consanguineous family with severely vacuolated spermatozoa. The analysis revealed a novel homozygous c.520A>G (p.Thr174Ala) variant in the archaelysin family metallopeptidase 2 ( AMZ2 ), a gene that encodes a zinc metalloprotease previously shown to be highly expressed in the testes and sperm. Multiple algorithms predicted this variant to be a damaging mutation. Consistent with an autosomal recessive mode of inheritance, this variant was inherited from heterozygous parental carriers. To investigate the potential pathogenicity of the identified variant, we compared the AMZ2 expression in sperm cells from the patient with the AMZ2 variant and from a healthy control. Immunoblot analysis revealed that the homozygous missense variant in AMZ2 abolished AMZ2 expression in the spermatozoa. Our findings reveal a candidate causative gene for vacuolated spermatozoa.

A Case Report of Anesthetic Management of a Patient with Hallervorden–Spatz Disease Posted for Incision and Drainage of Rectus Sheath Hematoma

Pantothenate kinase-associated neurodegeneration (PKAN), also known as Hallervorden–Spatz disease, is a neurodegenerative disorder presenting with dystonia, cognitive impairment, rigidity, and mental deterioration. It has an autosomal recessive mode of inheritance, which usually presents in late childhood or early adolescence. Rigidity poses a challenge to an anesthesiologist in airway management. In this case report, we present the case of a 23-year-old male patient, a diagnosed case of Hallervorden–Spatz disease scheduled for incision and drainage of rectus sheath hematoma which occurred due to blunt trauma to the abdomen. Patients with PKAN who require general anesthesia may present with symptoms that influence perioperative anesthetic management as well as postoperative care.

BG10 A case of pachydermoperiostosis (primary hypertrophic osteoarthropathy)

Abstract We report a case of a 21-year-old man who was referred from the community with concern about persistent swollen and inflamed eyelids together with possible facial acne. He was known to have hypertrophic osteoarthropathy under the care of rheumatology for which he was on regular infliximab infusions. He had previously been treated with methotrexate (intolerant) azathioprine and adalimumab (lack of efficacy). He also had a long-standing history of inflammatory bowel disease and associated complications: iron-deficiency anaemia, previous choledochal cyst and biliary stricture, as well as previous deficiencies in vitamins B12, A and E. The patient was known to the genetics team, with prior genetic testing demonstrating that he is homozygous for a pathogenic SLC02A1 variant (c.1264_1265delAC). This gene encodes a prostaglandin transporter involved in mediating the uptake and clearance of prostaglandins in numerous tissues. On examination, he was found to have pronounced thickening of the facial skin, especially the forehead, alongside deep furrowing of the scalp. The eyelids were severely swollen and inflamed, with prominent straight eyelashes. There were milia present on the face predominantly on the brow and cheeks. There was clubbing of all digits on his hands and feet. The cutaneous findings were deemed all in keeping with pachydermoperiostosis. Pachydermoperiostosis, also known as primary/idiopathic hypertrophic osteoarthropathy, Touraine–Solente–Gole syndrome and Rosenfeld–Kloepfer syndrome, was first described by Friedrich in 1868. This is a rare condition, and both autosomal dominant and autosomal recessive modes of inheritance have been noted. The condition usually presents during puberty and the hallmark features are thickening and coarsening of the facial skin, periostosis and digital clubbing. Other cutaneous features can include seborrhoea with sebaceous hyperplasia, acne, hyperhidrosis and cutis verticis gyrata. Ocular manifestations include blepharoptosis, floppy eyelid syndrome, and hypertrophy of both the eyelids and palpebral conjunctiva. Crohn disease and multiple bone and joint issues are known features of the condition (Doshi D. Touraine–Solente–Gole syndrome. Orbit 2018; 37:97–101; Tabatabaei SA, Masoomi A, Soleimani M et al. Pachydermoperiostosis: a clinicopathological description. J Curr Ophthalmol 2019; 31:450–3). This reported case demonstrates both classic cutaneous and other organ system features of this rare genetic condition. It highlights the importance of being able to recognize all the associated findings when a patient presents with thickening of their facial skin and eyelids.

BG06 Beyond keratin: when simplex is not so simple

Abstract Epidermolysis bullosa simplex (EBS) is a heterogeneous, congenital, mucocutaneous fragility syndrome, characterized ultrastructurally by cleavage within the basal keratinocyte. Seventy-five per cent of cases are attributable to mutations in KRT5 and KRT14, the vast majority of which are dominant negative mutations, resulting in impaired keratin intermediate filament dynamics within the basal layer of the epidermis. The presenting phenotype, including extracutaneous manifestations and overall severity, is often closely linked to the underlying genetic mutation; however, genotype–­phenotype correlation is poorly resolved in a minority of cases, and there is an approximately additional 15% of patients in whom genetic abnormalities are not identified. However, recent advances in next-generation sequencing technologies have expanded the mutational database. We describe two cases of EBS with rare underlying mutations and distinct clinical phenotypes. A 46-year-old man presented with widespread blistering primarily affecting his hands, feet, elbows and knees since childhood. He had unaffected, consanguineous parents and one of his three siblings was affected. Other presenting features included dystrophic nails, focal plantar keratoderma, truncal mottled pigmentation and large areas of hypopigmentation on the back. We considered a diagnosis of ‘EBS with mottled pigmentation’, but the autosomal recessive mode of inheritance and dystrophic nails were atypical. DNA whole-exome sequencing (WES) and bidirectional Sanger sequencing revealed a novel homozygous PLEC mutation [c.94dupG p.(Ala32GlyfsTer3)]. Pathogenic PLEC variants are known to cause autosomal dominant EBS, the Ogna type (MIM131950), autosomal recessive EBS with muscular dystrophy (MIM226670) and autosomal recessive EBS with pyloric atresia (MIM612138). To date, our patient has not manifested any signs of progressive muscle weakness, but the presenting age can vary. The second patient was a 30-year-old woman who presented with blistering on her flexures, feet, hands and friction sites since the age of 4 months. She had unaffected, consanguineous parents and eight unaffected siblings. WES and confirmatory bidirectional Sanger sequencing identified a homozygous nonsense mutation in DST [c.3370C>T p.(Gln1124Ter)]. DST encodes the epithelial isoform of bullous pemphigoid antigen-1, present in the skin, muscle and neuronal tissues. Only 11 patients with DST mutation-induced EBS have been reported to date. The cutaneous phenotype is reported to be blisters, postinflammatory dyspigmentation, scarring, nail dystrophy, keratoderma and hyperhidrosis. If the affected exon is present in neuronal isoforms and neuronal tissue, neurological symptoms are expected. Unlike the patient reported elsewhere who harbours exactly the same mutation, our patient has reported no neurological issues to date. These cases highlight the importance of unravelling genotype–phenotype correlation in rare autosomal recessive forms of EBS, with possible implications for future prognosis and management.

Autosomal recessive hyposegmentation of granulocytes in Australian Shepherd Dogs indicates a role for LMBR1L in myeloid leukocytes.

Pelger-Huët anomaly (PHA) in humans is an autosomal dominant hematological phenotype without major clinical consequences. PHA involves a characteristic hyposegmentation of granulocytes (HG). Human PHA is caused by heterozygous loss of function variants in the LBR gene encoding lamin receptor B. Bi-allelic variants and complete deficiency of LBR cause the much more severe Greenberg skeletal dysplasia which is lethal in utero and characterized by massive skeletal malformation and gross fetal hydrops. HG phenotypes have also been described in domestic animals and homology to human PHA has been claimed in the literature. We studied a litter of Australian Shepherd Dogs with four stillborn puppies in which both parents had an HG phenotype. Linkage analysis excluded LBR as responsible gene for the stillborn puppies. We then investigated the HG phenotype in Australian Shepherd Dogs independently of the prenatal lethality. Genome-wide association mapped the HG locus to chromosome 27 and established an autosomal recessive mode of inheritance. Whole genome sequencing identified a splice site variant in LMBR1L, c.191+1G>A, as most likely causal variant for the HG phenotype. The mutant allele abrogates the expression of the longer X2 isoform but does not affect transcripts encoding the shorter X1 isoform of the LMBR1L protein. The homozygous mutant LMBR1L genotype associated with HG is common in Australian Shepherd Dogs and was found in 39 of 300 genotyped dogs (13%). Our results point to a previously unsuspected function of LMBR1L in the myeloid lineage of leukocytes.

A FANCA mutation carrier with enhanced toxicity to cancer directed treatment - A case report and review of literature

Chemotherapy and radiotherapy are backbones of cancer treatment. Genome instability syndromes are rare but an essential factor to be identified early in the treatment of malignancies. It can lead to the occurrence of multiple malignancies and impede treatment due to undue hypersensitivity, leading to extreme and often fatal toxicities. We, hereby, report a case of a middle-aged lady who was diagnosed with a carcinoma of the head and neck and planned for treatment with neoadjuvant chemotherapy followed by surgery or chemoradiation. However, she developed severe toxicity to all forms of treatment for cancer. Her gene-based panel screening test revealed a Fanconi anaemia, complementation group A (FANCA) gene abnormality which is associated with an autosomal recessive mode of inheritance. This case outlines the importance of considering the possibility and a high index of suspicion of a hereditary basis in cases of relatively early-onset malignancy before defining an oncological treatment strategy. The paucity of data except for case reports limits evidence-based management in such cases and requires a collective effort for treatment.

Spectrum of genetic disorders and gene variants in the United Arab Emirates national population: insights from the CTGA database.

Like many other Arab countries, the United Arab Emirates (UAE) has a relatively high prevalence of genetic disorders. Here we present the first review and analysis of all genetic disorders and gene variants reported in Emirati nationals and hosted on the Catalogue for Transmission Genetics in Arabs (CTGA), an open-access database hosting bibliographic data on human gene variants associated with inherited or heritable phenotypes in Arabs. To date, CTGA hosts 665 distinct genetic conditions that have been described in Emiratis, 621 of which follow a clear Mendelian inheritance. Strikingly, over half of these are extremely rare according to global prevalence rates, predominantly with an autosomal recessive mode of inheritance. This is likely due to the relatively high consanguinity rates within the Emirati population. The 665 conditions include disorders that are unique to the Emirati population, as well as clearly monogenic disorders that have not yet been mapped to a causal genetic locus. We also describe 1,365 gene variants reported in Emiratis, most of which are substitutions and over half are classified as likely pathogenic or pathogenic. Of these, 235 had not been reported on the international databases dbSNP and Clinvar, as of December 2022. Further analysis of this Emirati variant dataset allows a comparison of clinical significance as reported by Clinvar and CTGA, where the latter is derived from the study cited. A total of 307 pathogenic/likely pathogenic variants from CTGA's Emirati dataset, were classified as benign, variants of uncertain significance, or were missing a clinical significance or had not been reported by Clinvar. In conclusion, we present here the spectrum of genetic disorders and gene variants reported in Emiratis. This review emphasizes the importance of ethnic databases such as CTGA in addressing the underrepresentation of Arab variant data in international databases and documenting population-specific discrepancies in variant interpretation, reiterating the value of such repositories for clinicians and researchers, especially when dealing with rare disorders.

Clinical Heterogeneity in Two Siblings Harbouring a Heterozygous PRPH2 Pathogenic Variant.

The aim of the study was to describe the clinical and genetic correlation of a c.469 G>A p.(Asp157Asn) heterozygous pathogenic variant in PRPH2 in two siblings of Italian origin. Both patients underwent ophthalmic examination, electrophysiological testing, autofluorescence imaging, and optical coherence tomography (OCT). Screening for pathogenic variants of the obtained DNA from the family members was carried out. The 52-year-old (♀, index patient) and 50-year-old (♂) siblings had BCVA (OD and OS) of 20/20 and 20/16 (♀) and 20/25 and 20/40 (♂), respectively, and suffered increased sensitivity to glare. Yellow irregular macular deposits, numerous small irregular hypo- and hyperreflective spots at the posterior pole, a patchy loss of photoreceptors, and retinal pigment epithelium (RPE) in the perifoveal region were seen. Electrophysiology showed dysfunction of rods and cones, with more affected cone dysfunction in the index patient, contrary to the generalised rod dysfunction in the brother of the index patient. The clinical, electrophysiological, and multimodal imaging findings of both siblings pointed towards Stargardt retinopathy with heterogenic presentation. The DNA analysis identified an autosomal dominant c.469 G>A p.(Asp157Asn) heterozygous pathogenic variant in PRPH2 associated with autosomal dominant cone-rod dystrophy and rod-cone dystrophy. PRPH2 codes for peripherin-2, a membrane protein that consists of 346 amino acids. Our findings confirm a heterogeneity in clinical presentation associated with pathogenic variants in PRPH2. It may follow either an autosomal dominant or an autosomal recessive mode of inheritance and show a very heterogeneous clinical manifestation of retinal degeneration, e.g., autosomal dominant retinitis pigmentosa (♂ sibling; II-3) and autosomal dominant cone-rod dystrophy (index ♀ sibling; II-2), autosomal dominant macular dystrophy, and also autosomal recessive retinitis pigmentosa.

Candidate causative variant for xanthinuria in a Domestic Shorthair cat.

Xanthinuria is a clinically significant form of urolithiasis in cats with poor clinical outcomes and limited treatment options. In humans, xanthinuria has an autosomal recessive mode of inheritance, with variants in xanthine dehydrogenase (XDH) and molybdenum cofactor sulfurase (MOCOS) responsible for cases. While causative genetic variants have not been identified in the domestic cat, a recessive mode of inheritance has been suggested. DNA was extracted from EDTA-stabilised blood obtained from a Domestic Shorthair cat with clinically confirmed xanthinuria. Whole-genome sequencing and variant assessment in XDH and MOCOS identified XDH:c.2042C>T (XDH:p.(A681V)) as a candidate causative variant for xanthinuria in this cat. The variant is located in a highly conserved part of the molybdenum-pterin co-factor domain, responsible for catalysing the hydroxylation of hypoxanthine to xanthine and uric acid. Variants in this domain of XDH have been shown to disrupt enzyme function and to cause xanthinuria in other species. When assessed in the wider cat population, the variant had an allele frequency of 15.8%, with 0.9% of the animals assessed homozygous for the alternative allele. Cats diagnosed with xanthinuria should be tested for this variant to validate its clinical relevance in the wider population.

Vitamin D dependent rickets type 2: a case-based review of patient with alopecia and rickets

Vitamin D dependent rickets (VDDR) type 2 is a very rare hereditary disease which has an autosomal recessive mode of inheritance. Patients with VDDR type 2 have a mutation in the gene encoding for vitamin D receptor on chromosome 12q12-q14, thus averting normal physiological action of 1,25 vitamin D. It's presents with the developmental delay in motor domain with features of rickets usually in the first year of life. Alopecia totalis has a frequent association with the disease. We are reporting a case of a 5-year-old boy who has a history of difficulty walking since 2 year of life, with a gradually progressive motor weakness course. Patients have a history of alopecia since 2 months of age, which progressed to alopecia totalis. On investigation, serum calcium was 7.2 mg/dl with a very high alkaline phosphate level of 1065 IU/ML with a normal vitamin D level was reported. The initial treatment started with IV calcium followed by 1000mg of oral calcium, along with a high dose of calcitriol. The patient was under periodic follow-up showing improvement in biochemical parameters. We reviewed literature of seven patient out of which 5 patients had alopecia and found 2 patients had enamel hypoplasia and all had features of rickets.

Identification and In Silico Analysis of a Homozygous Nonsense Variant in TGM1 Gene Segregating with Congenital Ichthyosis in a Consanguineous Family.

Background and Objectives: Lamellar ichthyosis is a rare skin disease characterized by large, dark brown plate-like scales on the entire body surface with minimum or no erythema. This phenotype is frequently associated with a mutation in the TGM1 gene, encoding the enzyme transglutaminase 1 which plays a catalytic role in the formation of the cornified cell envelop. The present study aimed to carry out clinical and genetic characterization of the autosomal recessive lamellar ichthyosis family from Balochistan. Materials and Methods: A consanguineous family with lamellar ichthyosis was enrolled from Balochistan, Pakistan. PCR amplification of all the exons and splice site junctions of the TGM1 gene followed by Sanger sequencing was performed on the genomic DNA. The identified variant was checked by In silico prediction tools to evaluate the effect of the variant on protein. Results: Sanger sequencing identified a homozygous nonsense variant c.131G >A (p.Trp44*) in the TGM1 gene that segregated in the autosomal recessive mode of inheritance in the family. The identified variant results in premature termination of transcribed mRNA and is predicted to cause a truncated or absent translation product transglutaminase-1 (TGase-1) accompanied by loss of catalytic activity, causing a severe clinical phenotype of lamellar ichthyosis in the patients. Conclusions: Here, we report a consanguineous lamellar ichthyosis family with a homozygous nonsense variant in the TGM1 gene. The variant is predicted as pathogenic by different In silico prediction tools.

The p.Pro2232Leu variant in the ChEL domain of thyroglobulin gene causes intracellular transport disorder and congenital hypothyroidism.

Thyroglobulin (TG), the predominant glycoprotein of the thyroid gland, functions as matrix protein in thyroid hormonegenesis. TG deficiency results in thyroid dyshormonogenesis. These variants produce a heterogeneous spectrum of congenital goitre, with an autosomal recessive mode of inheritance. The purpose of this study was to identify and functionally characterize new variants in the TG gene in order to increase the understanding of the molecular mechanisms responsible for thyroid dyshormonogenesis. A total of four patients from two non-consanguineous families with marked alteration of TG synthesis were studied. The two families were previously analysed in our laboratory, only one deleterious allele, in each one, was detected after sequencing the TG gene (c.2359 C > T [p.Arg787*], c.5560 G > T [p.Glu1854*]). These findings were confirmed in the present studies by Next-Generation Sequencing. The single nucleotide coding variants of the TG gene were then analyzed to predict the possible variant causing the disease. The p.Pro2232Leu (c.6695 C > T), identified in both families, showing a low frequency population in gnomAD v2.1.1 database and protein homology, amino acid prediction, and 3D modeling analysis predict a potential pathogenic effect of this variant. We also transiently express p.Pro2232Leu in a full-length rat TG cDNA clone and confirmed that this point variant was sufficient to cause intracellular retention of mutant TG in HEK293T cells. Consequently, each family carried a compound heterozygous for p.Arg787*/p.Pro2232Leu or p.Glu1854*/p.Pro2232Leu variants. In conclusion, our results confirm the pathophysiological importance of altered TG folding as a consequence of missense variants located in the ChEL domain of TG.

The Expansion of the Spectrum in Stuttering Disorders to a Novel ARMC Gene Family (ARMC3)

Stuttering is a common neurodevelopment speech disorder that negatively affects the socio-psychological dimensions of people with disability. It displays many attributes of a complex genetic trait, and a few genetic loci have been identified through linkage studies. Stuttering is highly variable regarding its phenotypes and molecular etiology. However, all stutters have some common features, including blocks in speech, prolongation, and repetition of sounds, syllables, and words. The involuntary actions associated with stuttering often involve increased eye blinking, tremors of the lips or jaws, head jerks, clenched fists, perspiration, and cardiovascular changes. In the present study, we recruited a consanguineous Pakistani family showing an autosomal recessive mode of inheritance. The exome sequencing identified a homozygous splice site variant in ARMC3 (Armadillo Repeat Containing 3) in a consanguineous Pashtun family of Pakistani origin as the underlying genetic cause of non-syndromic stuttering. The homozygous splice site variant (NM_173081.5:c.916 + 1G > A) segregated with the stuttering phenotype in this family. The splice change leading to the skipping of exon-8 is a loss of function (LoF) variant, which is predicted to undergo NMD (Nonsense mediated decay). Here, we report ARMC3 as a novel candidate gene causing the stuttering phenotype. ARMC3 may lead to neurodevelopmental disorders, including stuttering in humans.

A Missense Mutation (c.1037 G > C, p. R346P) in PAPSS2 Gene Results in Autosomal Recessive form of Brachyolmia Type 1 (Hobaek Form) in A Consanguineous Family.

Brachyolmia is a skeletal disorder with an autosomal mode of inheritance (both dominant and recessive) in which the patients have a short height, scoliosis and a reduced trunk size. From the Muzaffargarh District in Pakistan, a consanguineous family with multiple Brachyolmia-affected subjects were enrolled in the present study. Basic epidemiological data and radiographs were collected for the subjects. Whole exome sequencing (WES) which was followed by Sanger sequencing was applied to report the geneticbasic of Brachyolmia. The WES identified a missense mutation (c.1037 G > C, p. R346P) in exon 9 of the PAPSS2 gene that was confirmed by the Sanger sequencing in the enrolled subjects. The mutation followed a Mendalian pattern with an autosomal recessive inheritance mode. Multiple sequence alignment by Clustal Omega indicated that the PAPSS2 mutation-containing domain is highly conserved. The HEK293T whole-cell extract that was transfected with the Myc-tagged PCMV6-PAPSS2 of both the wild and mutant constructs were resolved by SDS-PAGE as well as by a Western blot, which confirmed that there are different PAPSS2 protein expression patterns when they were compared between the control and Brachyolmia patients. This difference between the normal and mutated protein was not evident when the three-dimensional computational structures were generated using homology modeling. We report a missense mutation (c.1037 G > C, p. R346P) in the PAPSS2 gene that caused Brachyolmia in a consanguineous Pakistani family.

Abstract 13579: TAX1BP3 -Encoding TAX1-Binding Protein 3 is a Novel Genetic Cause of Autosomal Recessive Arrhythmogenic Cardiomyopathy and Causes Pro-Arrhythmic Ryanodine Receptor 2-Mediated Calcium Leak

Introduction: Arrhythmogenic cardiomyopathy (AC) is a heart muscle disease where fibrofatty tissue replaces healthy myocardium. AC predisposes to ventricular arrhythmias and sudden cardiac death. We identified biallelic variants in the TAX1BP3- encoded tax1-binding protein 3 (TAX1BP3) in a genetically elusive family with AC. TAX1BP3 has putative roles in canonical Wnt signaling, but its function in the heart is unknown. Our goal is to identify novel mechanisms of AC development to develop therapeutics to mitigate or reverse disease progression. Hypothesis: We hypothesize that genetic loss of TAX1BP3 suppresses normal canonical Wnt-signaling in the heart, allowing pathologic remodeling and arrhythmogenesis associated with AC development. Methods: Whole exome sequencing of an AC genotype-negative family was performed. Induced pluripotent stem cells generated from peripheral blood mononuclear cells (PBMCs) from were differentiated into cardiac myocytes (iPSC-CMs) for 3 kindred. Line scans using CAL-520-labeled calcium were conducted with a Zeiss confocal microscope to capture calcium sparks after pacing iPSC-CMs. Sarcoplasmic reticulum store was measured after adding 10mM caffeine to iPSC-CMs. Adipogenesis in iPSC-CMs was visualized by immunofluorescence with Nile Red stain. Results: TAX1BP3 M78T/del variant co-segregates with AC in an autosomal recessive inheritance mode in an AC genotype-negative family. TAX1BP3 M78T/del PBMCs had reduced proliferation and qPCR from whole blood identified decreased canonical Wnt signaling. iPSC-CMs M78T/del have decreased intracellular calcium store, increased adipogenesis, and increased calcium leak associated with spontaneous calcium release events. Small molecule Wnt-activator BML-284 normalized calcium leak in iPSC-CMs M78T/del . Conclusions: Our results demonstrate that loss-of-function of TAX1BP3 is pro-arrhythmic and driven by calcium leak in iPSC-CMs which can be rescued by Wnt activation. We identified a new AC-associated gene, TAX1BP3, that has not been studied in the heart. Further studies are needed to explore the impact of TAX1BP3 on cardiac Wnt signaling, but our findings implicate Wnt activation as a possible treatment for AC - currently an untreatable, deadly disease.

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.

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.