Pathogenic TNNI1 variants disrupt sarcomere contractility resulting in hypo- and hypercontractile muscle disease.

Troponin I (TnI) regulates thin filament activation and muscle contraction. Two isoforms, TnI-fast (TNNI2) and TnI-slow (TNNI1), are predominantly expressed in fast- and slow-twitch myofibers, respectively. TNNI2 variants are a rare cause of arthrogryposis, whereas TNNI1 variants have not been conclusively established to cause skeletal myopathy. We identified recessive loss-of-function TNNI1 variants as well as dominant gain-of-function TNNI1 variants as a cause of muscle disease, each with distinct physiological consequences and disease mechanisms. We identified three families with biallelic TNNI1 variants (F1: p.R14H/c.190-9G>A, F2 and F3: homozygous p.R14C), resulting in loss of function, manifesting with early-onset progressive muscle weakness and rod formation on histology. We also identified two families with a dominantly acting heterozygous TNNI1 variant (F4: p.R174Q and F5: p.K176del), resulting in gain of function, manifesting with muscle cramping, myalgias, and rod formation in F5. In zebrafish, TnI proteins with either of the missense variants (p.R14H; p.R174Q) incorporated into thin filaments. Molecular dynamics simulations suggested that the loss-of-function p.R14H variant decouples TnI from TnC, which was supported by functional studies showing a reduced force response of sarcomeres to submaximal [Ca2+] in patient myofibers. This contractile deficit could be reversed by a slow skeletal muscle troponin activator. In contrast, patient myofibers with the gain-of-function p.R174Q variant showed an increased force to submaximal [Ca2+], which was reversed by the small-molecule drug mavacamten. Our findings demonstrated that TNNI1 variants can cause muscle disease with variant-specific pathomechanisms, manifesting as either a hypo- or a hypercontractile phenotype, suggesting rational therapeutic strategies for each mechanism.

Expanding the phenotypic spectrum of LHCGR signal peptide insertion variant: novel clinical and allelic findings causing Leydig cell hypoplasia type II.

PURPOSE: Leydig cell hypoplasia (LCH) type II is a rare disease with only a few cases reported. Patients presented with hypospadias, micropenis, undescended testes, or infertility. In this study, we report a new patient with compound heterozygous variants in the LHCGR gene and LCH type II phenotype. METHODS: Whole exome sequencing (WES) was performed followed by Sanger sequencing to confirm the detected variants in the patient and his parents. RESULTS: A novel missense variant (p.Phe444Cys) was identified in a highly conserved site and is verified to be in trans with the signal peptide's 33-bases insertion variant. CONCLUSION: Our research provides a more comprehensive clinical and genetic spectrum of Leydig cell hypoplasia type II. It highlighted the importance of WES in the diagnosis of this uncommon genetic disorder as well as the expansion of the genotype of LCH type II.

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.

Mutation analysis reveals novel and known mutations in SAG gene in first two Egyptian families with Oguchi disease.

BACKGROUND: Oguchi disease is a rare type of congenital stationary night blindness associated with an abnormal fundus appearance. It is inherited in an autosomal recessive manner where two types exist according to the gene affected; type 1 associated with S-antigen (SAG) gene mutations and type 2 associated with rhodopsin kinase (GRK1) gene mutations. PURPOSE: The aim of this work was to describe the clinical and genetic findings of the first two reported families of Oguchi disease in Egypt and African region. METHODS: Four members of two consanguineous Egyptian families with history of night blindness since childhood underwent complete ophthalmological examination, standard automated static perimetry, fundus color photography, fundus autofluorescence (FAF), fundus fluorescein angiography (FFA) in light-adapted state and spectral-domain optical coherence tomography (SD-OCT) of both the macula and the optic nerve head as well as central corneal thickness with repeated fundus photography following prolonged dark adaptation. Mutation screening of 7 coding exons of GRK1 gene and 15 coding exons of SAG gene as well as some flanking regions were performed using Sanger sequencing technique. The variants were tested for pathogenicity using different in silico functional analysis tools. RESULTS: The clinical examination and investigations confirmed Oguchi disease phenotype. One patient showed p.R193* (c.577C > T) which is a previously reported SAG gene mutation in a homozygous form. The other three patients from a different family showed (c.649-1 G > C), a novel canonical splice site SAG gene mutation in a homozygous form. CONCLUSION: The identification of the novel canonical splice site SAG gene variant in three members of the same family with clinically confirmed Oguchi disease reinforces its pathogenicity. A fourth patient from another family carried a previously reported mutation in the same gene. SAG gene variants may be the underlying genetic cause for Oguchi disease in Egypt. Our findings have expanded the spectrum of Oguchi disease-associated mutations in SAG gene and may serve as a basis for genetic diagnosis for Oguchi disease.

First Report of Two Egyptian Patients with Desbuquois Dysplasia due to Homozygous CANT1 Mutations.

Desbuquois dysplasia type 1 (DBQD1) is a very rare skeletal dysplasia characterized by growth retardation, short stature, distinct hand features, and a characteristic radiological monkey wrench appearance at the proximal femur. We report on 2unrelated Egyptian patients having the characteristic features of DBQD1 with different expressivity. Patient 1 presented at the age of 45 days with respiratory distress, short limbs, faltering growth, and distinctive facies while patient 2 presented at 5 years of age with short stature and hypospadias. The 2 patients shared radiological features suggestive of DBQD1. Whole-exome sequencing revealed a homozygous frameshift mutation in the CANT1 gene (NM_001159772.1:c.277_278delCT; p.Leu93ValfsTer89) in patient 1 and a homozygous missense mutation (NM_138793.4:c.898C>T; p.Arg300Cys) in patient 2. Phenotypic variability and variable expressivity of DBQD was evident in our patients. Hypoplastic scrotum and hypospadias were additional unreported associated findings, thus expanding the phenotypic spectrum of the disorder. We reviewed the main features of skeletal dysplasias exhibiting similar radiological manifestations for differential diagnosis. We suggest that the variable severity in both patients could be due to the nature of the CANT1 gene mutations which necessitates the molecular study of more cases for phenotype-genotype correlations.

Quaternary diagnostics scheme for mucolipidosis II and detection of novel mutation in GNPTAB gene.

BACKGROUND: Mucolipidosis II (ML II α/ß) is an inherited lysosomal storage disorder caused by deficiency of GlcNAc-phosphotransferase enzyme and results in mis-targeting of multiple lysosomal enzymes. Affected patients are characterized by skeletal deformities and developmental delay. Homozygous or compound heterozygous mutations in GNPTAB gene are associated with the clinical presentation. This is the first study to characterize the underlying genetics of ML among a cohort of Egyptian patients. ML II diagnosis established by clinical assessment, biochemical evaluation of enzymes, electron microscopy examination of gingival inclusion bodies, and molecular study of GNPTAB gene using targeted next-generation sequencing panel in 8 patients form 8 unrelated Egyptian families. RESULTS: Sequencing revealed 3 mutations in GNPTAB gene; 1 novel frame-shift mutation in exon 19 (c.3488_3488delC) and 2 previously reported mutations (c.1759C>T in exon 13 and c.3503_3504delTC in exon 19). All patients were homozygous for their corresponding mutations and the parents were consanguineous. CONCLUSIONS: According to the established quaternary diagnostic scheme, ML II was the final diagnosis in eight patients. The most common mutation was the frame shift c.3503_3504delTC mutation, found in 5 patients and associated with a severe phenotype.

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

Disorders/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.

Potential Value of miR-23a for Discriminating Neuromyelitis Optica Spectrum Disorder from Multiple Sclerosis.

BACKGROUND: Until now, no laboratory test or test set can guarantee the diagnosis of multiple sclerosis (MS) at early disease stages, and the disease symptoms may interfere with many other disease conditions. Analyzing the expression of circulating miRNAs may provide a useful approach for early and differential MS diagnosis. The main objective is assessment of the potential of serum miR-23a, miR-155, and miR-572 to differentiate between MS and other neuroinflammatory diseases. METHODS: Serum miRNAs were obtained from 37 MS patients and 25 healthy age-matched controls, along with patients with neuromyelitis optica spectrum disorder (NMOSD) [n = 13] and neuropsychiatric systemic lupus erythematosus (NPSLE) [n = 10]. miRNA expression levels were analyzed using real-time polymerase chain reaction (PCR) and pairwise comparisons were made to reveal the diagnostic/distinguishing potential of the analyzed miRNAs. RESULTS: In the study cohort, the three investigated miRNAs failed to display significant dysregulation in MS patients. However, they could significantly discriminate patients with NMOSD and NPSLE [median (IQR): 8.1 (6.1-9.2) and 8.8 (7.9-9.7) for miR-23a, 7.5 (5.3-8.3) and 8.0 (7.5-9.5) for miR-155 and 6.9 (5.0-8.8) and 6.4 (5.3-8.8) for miR-572 in NMOSD and NPSLE, respectively] from healthy subjects [median (IQR): 3.4 (1.5-4.3), 3.1 (1.1-5.6) and 3.5 (1.7-5.6) for miR-23a, miR-155 and miR-572, respectively], with area under the curve (AUC) ≤0.8. Remarkably, miR-23a has been emerging as a prospective biomarker for differentiation of MS from NMOSD as well as NPSLE (AUC<0.9). The miRNA combined use contributed to enhanced diagnostic and discriminatory performance in the study groups. CONCLUSION: Certain miRNA expression levels would contribute to discriminating MS from other neuroinflammatory diseases.

Assessment of the most common CYP21A2 point mutations in a cohort of congenital adrenal hyperplasia patients from Egypt.

Objectives Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is a common autosomal recessive disorder caused by defects in the CYP21A2 gene. We aimed to determine the prevalence of the most commonly reported mutations among 21-OHD Egyptian patients and correlate genotype with phenotype. Methods Molecular analysis of the CYP21A2 gene was performed for the detection of the six most common point mutations (p.P30L, p.I172N, p.V281L, p.Q318X, the splice site mutation Int2 [IVS2-13A/C>G], and the cluster of three mutations [p.I236N, p.V237E, and p.M239K] designed as CL6). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was performed on 47 unrelated Egyptian 21α-OH deficiency patients and their available parents to detect the presence of the six most common point mutations. Results Screening for the six most common point mutations in CYP21A2 gene, revealed mutations in 87.2% (82/94) of the studied alleles corresponding to 47 Egyptian patients. The most common mutation among the studied cases was IVS2-13C/A>G that was found to be presented in a frequency of 46.8% (44/94). The genotype/phenotype correlations related to null, A, and B groups were with PPV of 100, 55.5, and 83.3%, respectively. Conclusions The described method diagnosed CAH in 80.8% of the studied patients. Good correlation between genotype and phenotype in salt wasting and simple virilizing forms is determined, whereas little concordance is seen in nonclassical one. Furthermore, studying the carrier frequency of 21-OHD among the normal population is of great importance.

Extracellular miR-145, miR-223 and miR-326 expression signature allow for differential diagnosis of immune-mediated neuroinflammatory diseases.

BACKGROUND: Although misdiagnosis of neuromyelitis optica spectrum disorder (NMOSD) with neuropsychiatric systemic lupus erythematosus (NPSLE) or multiple sclerosis (MS) is not infrequent, reliable biomarkers remains an unmet need. Extracellular microRNAs (miRNAs) represent a worthy avenue to identify biomarkers for differential diagnosis. We aimed to explore the potential role of some selected circulating miRNAs as biomarkers for the differential diagnosis in immune-mediated neuroinflammatory diseases. METHODS: A total of 80 subjects were enrolled in the present study, including 37 patients with MS (relapsing-remitting MS [RRMS; n=18] and secondary progressive MS [SPMS; n=19]), 10 patients with NMOSD and 10 patients with NPSLE as well as 23 healthy subjects. Serum expression levels of three selected miRNAs (miR-145, miR-223 and miR-326) were measured using quantitative real-time polymerase chain reaction (qRT-PCR). Whole blood expression levels of cellular immune response-relevant target genes, including signaling mother against decapentaplegic peptide 3 (SMAD3) and specificity protein 1 (SP1), were also measured using qRT-PCR. RESULTS: In comparison to healthy subjects, only miR-145 and miR-223 were significantly up-regulated in MS patients, whereas, all the analyzed miRNAs revealed insignificant upregulation in NMOSD patients. All the examined miRNAs were significantly down-regulated in NPSLE patients compared to healthy subjects. miR-145, miR-223 and miR-326 expression profile is a promising diagnostic biomarker for MS and NPSLE, but not for NMOSD. This expression profile is capable of differentiating not only among MS, NMOSD and NPSLE, but also between RRMS and SPMS. CONCLUSION: Specific circulating miRNAs expression signature may have the potential to differentially diagnose immune-mediated neuroinflammatory diseases.

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

BACKGROUND: 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. AIM: 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. METHODS: Expression plasmids for wild-type 17ß-hydroxysteroid hydrogenase type 3 (17ß-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. OUTCOMES: Testosterone formation by wild-type and mutant 17ß-HSD3 enzymes was compared. RESULTS: Mutations T54A and L194P, despite normal protein expression, completely abolished 17ß-HSD3 activity, explaining their severe 46,XY DSD phenotype. Mutant M164T could still produce testosterone, albeit with significantly lower activity compared with wild-type 17ß-HSD3, resulting in ambiguous genitalia or a microphallus at birth. The substitution G289S represented a polymorphism exhibiting comparable activity to wild-type 17ß-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. CLINICAL TRANSLATION: Biochemical analysis of mutant 17ß-HSD3 enzymes is necessary to understand genotype-phenotype relationships. STRENGTHS AND LIMITATIONS: 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. CONCLUSION: The 17ß-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.

Four novel mutations in the N-acetylgalactosamine-6-sulfate sulfatase gene among Egyptian patients with Morquio A disease.

Morquio A disease (Mucopolysaccharidosis IVA, MPS IVA) is an autosomal recessive lysosomal storage disorder caused by deficient activity of the enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS) encoded by the GALNS gene. This deficiency leads to a decreased ability to degrade the glycosaminoglycans (GAGs) keratan sulfate and chondroitin 6-sulfate, thereby causing their accumulation within the lysosomes and consequently prominent skeletal and visceral abnormalities. Clinical evaluation and biochemical GALNS enzyme activity determination were carried out for the patients from four unrelated Egyptian families. Mutational analysis was performed to PCR products by sequencing of the 14 exons and exon-intron boundaries of GALNS gene for the 4 patients. Sequence analysis revealed four novel mutations; three nonsense mutations (p.Q12X, p.Q220X, p.Y254X) and one missense mutation, p.D40G. All four patients were offspring of consanguineous marriages and were homozygous for the corresponding mutation. The activity of the GALNS enzyme was below normal reference range in all of them. The p.Q12X and p.Y254X were associated with severe MPS IVA phenotype. Molecular analysis of GALNS gene revealed four novel mutations in four different Morquio A Egyptian patients.

WT1 Gene Mutation, p.R462W, in a 46,XY DSD Patient from Egypt with Gonadoblastoma and Review of the Literature.

WT1 gene mutations have been described in 46,XY patients with ambiguous genitalia or complete gonadal dysgenesis with or without Wilms' tumor, nephropathy, gonadoblastoma, and other defects, e.g., cryptorchidism or hypospadias. p.R462W is a hot spot mutation in exon 9 and is the most common mutation in patients with Denys-Drash syndrome. However, in this study we report an Egyptian patient with a novel phenotype carrying the p.R462W mutation. We also review the heterogeneity of phenotypes of previously reported patients with the p.R462W (previously referred to as Arg394Trp) mutation.

Identification of NR5A1 Mutations and Possible Digenic Inheritance in 46,XY Gonadal Dysgenesis.

The phenotypic spectrum of patients carrying NR5A1 mutations ranges from 46,XY gonadal dysgenesis to male infertility. Phenotypic variability could be due to digenic or oligogenic inheritance of pathogenic variants in other testis-determining genes. Here, exome sequencing identified 2 pathogenic de novo NR5A1 mutations in 2 patients with 46,XY gonadal dysgenesis, p.Q206Tfs*20 and p.Arg313Cys. The latter patient also carried a missense mutation in MAP3K1. Our data extend the number of NR5A1 gene mutations associated with gonadal dysgenesis. The combination of an NR5A1 mutation with a MAP3K1 variant may explain the phenotypic variability associated with NR5A1 mutations.

Mutational Profile of 10 Afflicted Egyptian Families with 17-ß-HSD-3 Deficiency.

This study aimed at the detection of HSD17B3 gene mutations in Egyptian patients with suspected diagnosis of 46,XY DSD due to 17-ß-HSD-3 deficiency and at evaluation of phenotype/genotype relationship of these mutations. The study was conducted on 11 patients of 10 families which were provisionally diagnosed to have 17-ß-HSD-3 enzyme deficiency. Karyotyping, hormonal evaluation of testosterone, x0394;4-androstenedione, and dihydrotestosterone, and sequencing analysis of the 11 exons of the HSD17B3 gene were done. Mutations in HSD17B3 were detected in exons 2, 7, 8, 10, and 11, and 6 novel mutations were determined in exons 1, 2, 7, and 8. Two patients showed compound heterozygous mutations, while 8 families had probands with homozygous mutations. The current study shows that 17-ß-HSD-3 deficiency is not an uncommon disorder among Egyptian DSD cases. It was evidenced that the mutational profile of the disease is rather heterogeneous, relatively different from those reported in other populations, and has a high degree of novel genetic defects.

Circulating miRNAs 21 and 221 as biomarkers for early diagnosis of prostate cancer.

To compare the expression of two promising circulating micro-ribonucleic acids (miRNAs 21 and 221) in patients with prostate cancer to subjects without cancer and to evaluate their potential role as specific noninvasive molecular biomarkers for prostate cancer diagnosis, circulating miRNAs 21 and 221 expression profiles were analyzed in 20 men aged 50-75 years, presenting with lower urinary tract symptoms (LUTSs) and undergoing transrectal ultrasound (TRUS)-guided prostate biopsy based on either elevated serum prostate-specific antigen (PSA) (>4.0 ng/ml) or suspicious digital rectal examination (DRE). The performance of miRNAs 21 and 221 in differentiating prostate cancer from nonmalignant cases was evaluated and compared to DRE and elevated PSA. miRNA 21 was overexpressed in 90 % of group A vs. 10 % of group B, while miRNA 221 was overexpressed in 80 % of group A vs. 20 % of group B (p = 0.001). MiRNA 21 overexpression had the highest performance as a diagnostic test with a sensitivity of 90 % and a specificity 90 % (p = 0.02). No correlations were noted between Gleason score of prostate cancer cases and relative quantity (RQ) 21 (r = -0.355, p = 0.292) or RQ 221 (r = -0.044, p = 0.892). Our study showed that serum miRNAs 21 and 221 expression profiling tests may be used as specific noninvasive molecular biomarkers for prostate cancer diagnosis due to their higher sensitivity and specificity with a high negative predictive value leading to a decrease in the biopsies taken for patients with elevated serum PSA values.

A novel mutation (c.2735_2736delTC) in the androgen receptor gene in 46,XY females with complete androgen insensitivity syndrome in an Egyptian family.

BACKGROUND: Androgen insensitivity syndrome (AIS) results from resistance of the target tissues to the effect of the androgenic hormones producing a phenotype with varying degrees of feminization ranging from male infertility to completely normal female external genitalia. Androgen receptor (AR) is a transcription factor that interacts with the androgenic steroids that act as ligands activating the AR, and via different cellular mechanisms, the activated AR binds to the DNA of target tissues to induce the desired biological changes. To date, more than 800 different mutations in the AR gene have been identified in patients with AIS and the majority of these mutations are localized in the ligand-binding domain. METHODS: Here we describe an Egyptian family with 7 affected 46,XY females with complete androgen insensitivity. RESULTS: Mutational analysis of the AR gene revealed a novel frameshift mutation in exon 8 of the gene c.2735_2736delTC. CONCLUSION: This study extends the number of AR gene mutations identified so far. Further, it confirms that AR gene mutations are the most frequent cause of 46,XY disorder of sexual development, with higher frequency in the complete phenotype.

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

BACKGROUND/PURPOSE: 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.

Molecular prenatal diagnosis of autosomal recessive childhood spinal muscular atrophies (SMAs).

Autosomal recessive childhood spinal muscular atrophy (SMAs) is the second most common neuromuscular disorder and a common cause of infant disability and mortality. SMA patients are classified into three clinical types based on age of onset, and severity of symptoms. About 94% of patients have homozygous deletion of exon 7 in survival motor neuron (SMN1) gene. The neuronal apoptosis inhibitory protein (NAIP) gene was found to be more frequently deleted in the severest form of the disease. This study aimed to comment on the implementation of genetic counseling and prenatal diagnosis of SMAs for 85 fetuses from 75 Egyptian couples at risk of having an affected child. The homozygous deletion of exon 7 in SMN1 gene and the deletion of exon 5 of the NAIP gene were detected using PCR-REFLP and multiplex PCR methods respectively. Eighteen fetuses showed homozygous deletion of exon 7 in SMN1 gene and deletion of exon 5 in NAIP gene. In conclusion prenatal diagnosis is an important tool for accurate diagnosis and genetic counseling that help decision making in high risk families.

Isodicentric Y chromosomes in Egyptian patients with disorders of sex development (DSD).

Isodicentric chromosome formation is the most common structural abnormality of the Y chromosome. As dicentrics are mitotically unstable, they are subsequently lost during cell division resulting in mosaicism with a 45,X cell line. We report on six patients with variable signs of disorders of sex development (DSD) including ambiguous genitalia, short stature, primary amenorrhea, and male infertility with azoospermia. Cytogenetic studies showed the presence of a sex chromosome marker in all patients; associated with a 45,X cell line in five of them. Fluorescence in situ hybridization (FISH) technique was used to determine the structure and the breakage sites of the markers that all proved to be isodicentric Y chromosomes. Three patients, were found to have similar breakpoints: idic Y(qter→ p11.32:: p11.32→ qter), two of them presented with ambiguous genitalia and were found to have ovotesticular DSD, while the third presented with short stature and hypomelanosis of Ito. One female patient presenting with primary amenorrhea, Turner manifestations and ambiguous genitalia revealed the breakpoint: idic Y (pter→q11.1::q11.1→pter). The same breakpoint was detected in a male with azoospermia but in non-mosaic form. An infant with ambiguous genitalia and mixed gonadal dysgenesis (MGD) had the breakpoint at Yq11.2: idic Y(pter→q11.2::q11.2→pter). SRY signals were detected in all patients. Sequencing of the SRY gene was carried out for three patients with normal results. This study emphasizes the importance of FISH analysis in the diagnosis of patients with DSD as well as the establishment of the relationship between phenotype and karyotype.