Novel Sequence Variants in the NPC1 Gene in Egyptian Patients with Niemann-Pick Type C

BACKGROUND: Niemann-Pick disease type C (NPC) is a rare, autosomal recessive, progressive neuro-visceraldisease caused by biallelic mutations in either NPC1gene (95% of cases) or NPC2 gene. AIM: This caseseries study aimed at the molecular analysis of certain hot spots of NPC1 genein NPC Egyptian patients. METHODS: The study included 15 unrelated NPC patients and selected parents,as well as20 healthy controls of matched sex and age. Clinical investigations were performed according to well established clinical criteria. Assessment of the chitotriosidase level, as an initial screening tool for NPC, was done in all cases. Polymerase chain reaction amplification of NPC1 exons (17–25) encountering the hotspot residues (855–1098 and1038–1253) was carried out followed by direct sequencingfor mutational analysis. RESULTS: All includedpatients with mainly neurovisceral involvement were characterized. The onset of the disease varied from early-infantile (58.3%) to late-infantile (26.7%) and juvenile-onset (6.7%). Ahigh chitotriosidase level wasobservedin all patients. Molecular analysis of NPC1 (exons 17–25) confirmed 15 mutant alleles out of 30 studied ones. They included two novel homozygous missense variants (p.Ser1169Arg and p.Ser1197Phe) and previously reportedfour mutations (p.Arg958*, p.Gly910Ser, p.Ala927Glyfs*38, and andp.Cys1011*). CONCLUSION: The two studied amino acid residues (855–1098 and 1038–1253) could beconsidered aspotential hotspot regions in NPC1 Egyptian patients

Advances in genomic diagnosis of a large cohort of Egyptian patients with disorders of sex development

International audienceDisorders/differences of sex development (DSD) comprise a group of congenital disorders that affect the genitourinary tract and usually involve the endocrine and reproductive system. The aim of this work was to identify genetic variants responsible for disorders of human urogenital development in a cohort of Egyptian patients. This three-year study included 225 patients with various DSD forms, referred to the genetic DSD and endocrinology clinic, National Research Centre, Egypt. The patients underwent thorough clinical examination, hormonal and imaging studies, detailed cytogenetic and fluorescence in situ hybridization analysis, and molecular sequencing of genes known to commonly cause DSD including AR, SRD5A2, 17BHSD3, NR5A1, SRY, and WT1. Whole exome sequencing (WES) was carried out for 18 selected patients. The study revealed a high rate of sex chromosomal DSD (33%) with a wide array of cytogenetic abnormalities. Sanger sequencing identified pathogenic variants in 33.7% of 46,XY patients, while the detection rate of WES reached 66.7%. Our patients showed a different mutational profile compared with that reported in other populations with a predominance of heritable DSD causes. WES identified rare and novel pathogenic variants in NR5A1, WT1, HHAT, CYP19A1, AMH, AMHR2, and FANCA and in the X-linked genes ARX and KDM6A. In addition, digenic inheritance was observed in two of our patients and was suggested to be a cause of the phenotypic variability observed in DSD

Mutational analysis of the PTPN11 gene in Egyptian patients with Noonan syndrome

Noonan syndrome (NS) is inherited as an autosomal dominant disorder with dysmorphic facies, short stature, and cardiac defects, which can be caused by missense mutations in the protein tyrosine phosphatase nonreceptor type 11 (PTPN11) gene, which encodes src homology region 2 domain containing tyrosine phosphatase-2 (SHP-2), a protein tyrosine phosphatase that acts in signal transduction downstream to growth factors and cytokines. The current study aimed to study the molecular characterization of the PTPN11 gene among Egyptian patients with Noonan syndrome. Methods: Eleven exons of the PTPN11 gene were amplified and screened by single stranded conformational polymorphism (SSCP). DNA samples showing band shift in SSCP were subjected to sequencing. Results: Mutational analysis of the PTPN11 gene revealed T→C transition at position 854 in exon 8, predicting Phe285Ser substitution within PTP domain of SHP-2 protein, in one NS patient and –21C→T polymorphism in intron 7 in four other cases. Conclusion: Knowing that NS is phenotypically heterogeneous, molecular characterization of the PTPN11 gene should serve to establish NS diagnosis in patients with atypical features, although lack of a mutation does not exclude the possibility of NS

Biochemical Analysis of Four Missense Mutations in the HSD17B3 Gene Associated With 46,XY Disorders of Sex Development in Egyptian Patients

Mutations in the HSD17B3 gene are associated with a 46,XY disorder of sexual development (46,XY DSD) as a result of low testosterone production during embryogenesis.; To elucidate the molecular basis of the disorder by chemically analyzing four missense mutations in HSD17B3 (T54A, M164T, L194P, G289S) from Egyptian patients with 46,XY DSD.; Expression plasmids for wild-type 17β-hydroxysteroid hydrogenase type 3 (17β-HSD3) and mutant enzymes generated by site-directed mutagenesis were transiently transfected into human HEK-293 cells. Protein expression was verified by western blotting and activity was determined by measuring the conversion of radiolabeled Δ4-androstene-3,17-dione to testosterone. Application of a homology model provided an explanation for the observed effects of the mutations.; Testosterone formation by wild-type and mutant 17β-HSD3 enzymes was compared.; Mutations T54A and L194P, despite normal protein expression, completely abolished 17β-HSD3 activity, explaining their severe 46,XY DSD phenotype. Mutant M164T could still produce testosterone, albeit with significantly lower activity compared with wild-type 17β-HSD3, resulting in ambiguous genitalia or a microphallus at birth. The substitution G289S represented a polymorphism exhibiting comparable activity to wild-type 17β-HSD3. Sequencing of the SRD5A2 gene in three siblings bearing the HSD17B3 G289S polymorphism disclosed the homozygous Y91H mutation in the former gene, thus explaining the 46,XY DSD presentations. Molecular modeling analyses supported the biochemical observations and predicted a disruption of cofactor binding by mutations T54A and M164T and of substrate binding by L196P, resulting in the loss of enzyme activity. In contrast, the G289S substitution was predicted to disturb neither the three-dimensional structure nor enzyme activity.; Biochemical analysis of mutant 17β-HSD3 enzymes is necessary to understand genotype-phenotype relationships.; Biochemical analysis combined with molecular modeling provides insight into disease mechanism. However, the stability of mutant proteins in vivo cannot be predicted by this approach.; The 17β-HSD3 G289S substitution, previously reported in other patients with 46,XY DSD, is a polymorphism that does not cause the disorder; thus, further sequence analysis was required and disclosed a mutation in SRD5A2, explaining the cause of 46,XY DSD in these patients. Engeli RT, Tsachaki M, Hassan HA, et al. Biochemical Analysis of Four Missense Mutations in the HSD17B3 Gene Associated With 46,XY Disorders of Sex Development in Egyptian Patients. J Sex Med 2017;14:1165-1174

Clinical and molecular spectrum of a large Egyptian cohort with ALS2‐related disorders of infantile‐onset of clinical continuum IAHSP/JPLS

This study presents 46 patients from 23 unrelated Egyptian families with ALS2-related disorders without evidence of lower motor neuron involvement. Age at onset ranged from 10 months to 2.5 years, featuring progressive upper motor neuron signs. Detailed clinical phenotypes demonstrated inter- and intrafamilial variability. We identified 16 homozygous disease-causing ALS2 variants; sorted as splice-site, missense, frameshift, nonsense and in-frame in eight, seven, four, three, and one families, respectively. Seven of these variants were novel, expanding the mutational spectrum of the ALS2 gene. As expected, clinical severity was positively correlated with disease onset (p = 0.004). This work provides clinical and molecular profiles of a large single ethnic cohort of patients with ALS2 mutations, and suggests that infantile ascending hereditary spastic paralysis (IAHSP) and juvenile primary lateral sclerosis (JPLS) are belonged to one entity with no phenotype-genotype correlation