The utility of whole-exome sequencing in accurate diagnosis of neuromuscular disorders in consanguineous families in Jordan.

BACKGROUND: Neuromuscular disorders (NMDs) encompass a large group of genetic and acquired diseases affecting muscles, leading to progressive muscular weakness. These disorders are frequently inherited in an autosomal-recessive (AR) pattern with extreme heterogeneity and various clinical presentations. Consanguinity increases the likelihood of AR disorders, with high rates of cousin inbreeding in Jordan and other Arab countries. In Jordan, the implementation of genetic diagnosis is limited, with delayed or misdiagnosis of genetic disorders. Thus, the lack of genetic counselling and specialized treatment options is frequently encountered in the country. METHODS: Whole-exome sequencing (WES) was conducted for eleven probands from ten Jordanian families who have been formerly diagnosed with limb-girdle dystrophy (LGMD) and Charcot-Marie-Tooth disease (CMT). The previous diagnoses were established principally on clinical examination in the absence of genetic testing. Additionally, Sanger sequencing and segregation analysis were used to validate the resulted pathogenic variants. RESULTS: Multiple variants were identified using WES: For DYSF gene, a missense variant (c. 4076 T > C, p.Leu1359Pro) in exon 38; a nonsense variant (c. 4321C > T, p.Gln1441Ter) in exon 39; a single-nucleotide deletion (c. 5711delG, p.Gly1904AlafsTer101) in exon 51. Other variants included a missense variant (c. 122G > A, p.Arg41Gln) in exon 3 of MPV17 gene, a single-nucleotide deletion (c. 859 delC, p.Lue287Ser fs14*) in exon 6 of SGCB gene, a missense variant (c. 311G > A, p.Gly104Asp) in exon 2 of SLC25A46 gene, a nonsense variant (c. 496C > T, p.Arg166Ter) in exon 5 of SGCG gene, and a nonsense variant (c.3202C > T, p.Gln1068Ter) in exon 13 of SH3TC2 gene. CONCLUSION: Utilization of WES is helpful to facilitate rapid and accurate NMDs diagnosis, complementing a thorough clinical evaluation. This approach can be invaluable to aid in the identification of genetic risks among consanguineous couples. Subsequently, well-informed genetic counselling and potential individualized treatment can be provided.

Establishment of a human induced pluripotent stem cell line, JUCTCi012-A, from multiple symmetric lipomatosis (MSL) patient carrying a homozygous Arg707Trp (c.2119C > T) mutation in the MFN2 gene.

Induced pluripotent stem cells (iPSCs) were generated from skin fibroblasts collected from a 39-year-old multiple symmetric lipomatosis (MLS) female patient carrying a point mutation in MFN2 gene (c.2119C > T). The resulting iPSCs showed typical embryonic-like morphology, expressed pluripotency stem cell markers, retained the normal karyotype after reprogramming and showed the potential to differentiate into three germ layers. This iPSC line can be used for studying MSL disease mechanisms.

Generation and characterization of induced pluripotent stem cell (iPSC) line (JUCTCi002-A) from a patient with ataxia with oculomotor apraxia type 1 (AOA1) harboring a homozygous mutation in the APTX gene.

Ataxia with Oculomotor Apraxia Type 1 (AOA1) is an autosomal-recessive cerebellar ataxia characterized by early-onset cerebellar atrophy and axonal sensorimotor polyneuropathy. AOA1 is related to mutations in the aprataxin (APTX) gene encoding for the aprataxin protein. The aprataxin protein has been reported to be involved in DNA single-strand break repair (SSBR) machinery and it localizes to the mitochondria to preserve the mitochondrial function. Here, we demonstrate the generation of induced pluripotent stem cell (iPSC) line (JUCTCi002-A) from AOA1 patient's skin dermal fibroblasts. The selected line showed normal karyotype, expression of pluripotency markers and the ability to differentiatie in vitro into the three germ layers.

Identification of APTX disease-causing mutation in two unrelated Jordanian families with cerebellar ataxia and sensitivity to DNA damaging agents.

BACKGROUND: Ataxia with oculomotor apraxia type 1 (AOA1) is a rare autosomal recessive cerebellar ataxia, caused by mutations in the APTX gene. The disease is characterized by early-onset cerebellar ataxia, oculomotor apraxia and severe axonal polyneuropathy. The aim of this study was to detect the disease-causing variants in two unrelated consanguineous Jordanian families with cerebellar ataxia using whole exome sequencing (WES), and to correlate the identified mutation(s) with the clinical and cellular phenotypes. METHODS: WES was performed in three affected individuals and segregation analysis of p.W279* APTX candidate variant was performed. Expression levels of APTX were measured in patients' skin fibroblasts and peripheral blood mononuclear cells, followed by western blot analysis in skin fibroblasts. Genotoxicity assay was performed to detect the sensitivity of APTX mutated cells to H2O2, MMC, MMS and etoposide. RESULTS: A recurrent homozygous nonsense variant in APTX gene (c.837G>A, p.W279*) was revealed in all affected individuals. qRT-PCR showed normal APTX levels in peripheral blood and lower levels in fibroblast cells. However, western blot showed the absence of APTX protein in patients' skin fibroblasts. Significant hypersensitivity to H2O2, MMC and etoposide and lack of sensitivity to MMS were noted. CONCLUSIONS: This is the first study to report the identification of a nonsense variant in the APTX gene (c.837G>A; p.W279*) in AOA1 patients within the Jordanian population. This study confirmed the need of WES to assist in the diagnosis of cerebellar ataxia and it emphasizes the importance of studying the pathophysiology of the APTX gene.

Establishment of (JUCTCi007-A) iPSC line from a patient with congenital myasthenic syndrome (CMS) carrying a homozygous mutation p.Arg331Trp (c.991C > T) in the CHRNE gene.

Induced pluripotent stem cells (iPSCs) were generated from skin fibroblasts obtained from a 24-year-old female diagnosed with hereditary congenital myasthenic syndrome (CMS), caused by p.Arg331Trp (c.991C > T) homozygous mutation in the gene coding for the epsilon subunit of the acetylcholine receptor (CHRNE). The generated iPSCs shared similar karyotype with the parental dermal fibroblast cells, expressed pluripotency stem cell markers, and demonstrated differentiation potential into the three germ layers. This cell line can be used as an ideal model to facilitate the understanding of the pathogenic disease mechanisms underlying the congenital myasthenic syndrome and for developing novel therapeutic strategies.