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Biomedical subjects

Ahmad S Teebi

Publications and source records attributed to Ahmad S Teebi.

At least 19 recordsLinked to original sources
PubMed2007

Severe hypertelorism, midface prominence, prominent/simple ears, severe myopia, borderline intelligence, and bone fragility in two brothers: new syndrome?

We report on two brothers, born to double first cousin Jordanian Arab parents, with a syndrome comprising severe hypertelorism with upslanted palpebral fissures, brachycephaly, abnormal ears, sloping shoulders, enamel hypoplasia, and osteopenia with repeated fractures. Both have severe myopia, mild to moderate sensori-neural hearing loss and borderline intelligence. Results of chromosome analysis were normal as was a FISH assay for subtelomeric rearrangements. The father has mild hypertelorism but the family history is otherwise unremarkable. We think that this represents a previously unrecognized autosomal or X-linked recessive syndrome.

Bone Diseases, Developmental↗
PubMed2006

Defective glycosylation of decorin and biglycan, altered collagen structure, and abnormal phenotype of the skin fibroblasts of an Ehlers-Danlos syndrome patient carrying the novel Arg270Cys substitution in galactosyltransferase I (beta4GalT-7).

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders affecting skin and joint function. Molecular defects in extracellular matrix proteins, including collagen (type I, III, and V) and tenascin X are associated with different forms of EDS. Compound heterozygous mutations in the B4GALT7 gene, resulting in aberrant glycosylation of the dermatan sulfate proteoglycan decorin, had been described in a single patient affected with the progeroid form of EDS. We have studied the molecular phenotype of decorin, biglycan, and collagen type I containing fibrils in skin fibroblasts of a patient carrying the novel homozygous C808T point mutation in the B4GALT7 gene, which causes an Arg270Cys substitution in beta4GalT-7. Compared to control fibroblasts, galactosyltransferase activity in beta4GalT-7(Arg270Cys) cells was approximately three times reduced over a temperature range of 25-41 degrees C. Pulse-chase experiments and confocal microscopy demonstrated that synthesis and secretion of decorin were normal in beta4GalT-7(Arg270Cys) cells. However, about 50% of decorin were synthesized as a protein core in addition to its proteoglycan form. Biglycan was found in a monoglycanated form in addition to its mature form. Glycosaminoglycan chains were of the dermatan/chondroitin sulfate type both in beta4GalT-7(Arg270Cys) and control cells, and epimerization was reduced for decorin and biglycan. Compared to control cells, beta4GalT-7(Arg270Cys) cells showed altered, highly spread or stretched phenotypes and decreased proliferation rates. At the ultrastructural level, an intracellular accumulation of multiple secondary lysosomes and degenerative vacuoles was seen in beta4GalT-7(Arg270Cys) cells. Furthermore, the collagen suprastructures were altered in the beta4GalT-7(Arg270Cys) cells. The reduced beta4GalT-7 activity resulting in defective glycosylation of decorin and biglycan may be responsible for the complex molecular pathology in beta4GalT-7 deficient EDS patients, given the role of these proteoglycans in bone formation, collagen fibrillogenesis, and skeletal muscle development.

Arginine↗
PubMed2005

Genetic diversity among the Arabs.

The Arabs in general are genetically diverse. Major factors that contributed to their diversity include the migrations of Semitic tribes from the Arabian Peninsula, the Islamic expansion in the 7th century AD, the Crusade wars and the recent migration dynamics. These events have resulted in the admixture of the original Arabs with other populations extending from east and south Asia to Europe and Africa. Their demographic features include high rates of consanguinity, a large family size and a rapid population growth. There is a high frequency of autosomal recessive disorders and increased frequencies of homozygosity for autosomal dominant traits, such as familial hypercholesterolemia and X-linked traits, such as glucose-6-phosphate dehydrogenase deficiency. The patterns of autosomal recessive disorders, including their mutations, may be different in various geographic locations within the Arab world. However, there are disorders that are specifically prevalent among the Arabs either uniformly or in certain locations. The Arab Genetic diseases include Bardet-Biedl syndrome, Meckel syndrome, autosomal recessive severe childhood muscular dystrophy, osteopetrosis and renal tubular acidosis, Sanjad-Sakati syndrome and others.

Arabs↗
PubMed2004

Newly recognized autosomal recessive acrofacial dysostosis syndrome resembling Nager syndrome.

We report on two patients with a unique constellation of anomalies resembling the Nager acrofacial dysostosis syndrome. Clinical manifestations which differentiate their condition from Nager syndrome include: microcephaly, cleft lip and palate, a peculiar beaked nose, blepharophimosis, microtia, symmetrical involvement of the thumbs, and great toes and developmental delay. We postulate that the inheritance is autosomal recessive on the basis of similarly affected male and female sibs.

Abnormalities, Multiple↗
PubMed2003

Alopecia congenita universalis, microcephaly, cutis marmorata, short stature and XY gonadal dysgenesis: variable expression of El-Shanti syndrome.

UNLABELLED: Alopecia congenita, laryngomalacia, and XY gonadal dysgenesis has been reported recently as a new syndrome in two unrelated Arab families from Jordan. We report a 4-year-old girl of first cousin Arab parents who had alopecia, microcephaly, cutis marmorata, short stature and borderline cognitive development. Karyotype analysis revealed a male constitution (46,XY) with no deletion of STSor SRY. She showed entirely normal female external genitalia and absence of female internal genitalia. Histological examination of the very small testicles found on laparascopy showed developed spermatic cords and paratesticular tissue with no testicular parenchyma, no Sertoli or Leydig cell development, and no seminiferous tubular development. Hormonal profile was that of a normal female child. Southern blotting and PCR assays showed an intact Y chromosome. Limited sequencing of the SRYgene revealed no mutations. CONCLUSION: this patient, together with the recently reported consanguineous families, represent a previously unrecognised autosomal recessive trait with pleiotropic effects including XY gonadal dysgenesis.

Abnormalities, Multiple↗
PubMed2003

Mutations in capillary morphogenesis gene-2 result in the allelic disorders juvenile hyaline fibromatosis and infantile systemic hyalinosis.

Juvenile hyaline fibromatosis (JHF) and infantile systemic hyalinosis (ISH) are autosomal recessive syndromes of unknown etiology characterized by multiple, recurring subcutaneous tumors, gingival hypertrophy, joint contractures, osteolysis, and osteoporosis. Both are believed to be allelic disorders; ISH is distinguished from JHF by its more severe phenotype, which includes hyaline deposits in multiple organs, recurrent infections, and death within the first 2 years of life. Using the previously reported chromosome 4q21 JHF disease locus as a guide for candidate-gene identification, we identified and characterized JHF and ISH disease-causing mutations in the capillary morphogenesis factor-2 gene (CMG2). Although CMG2 encodes a protein upregulated in endothelial cells during capillary formation and was recently shown to function as an anthrax-toxin receptor, its physiologic role is unclear. Two ISH family-specific truncating mutations, E220X and the 1-bp insertion P357insC that results in translation of an out-of-frame stop codon, were generated by site-directed mutagenesis and were shown to delete the CMG-2 transmembrane and/or cytosolic domains, respectively. An ISH compound mutation, I189T, is predicted to create a novel and destabilizing internal cavity within the protein. The JHF family-specific homoallelic missense mutation G105D destabilizes a von Willebrand factor A extracellular domain alpha-helix, whereas the other mutation, L329R, occurs within the transmembrane domain of the protein. Finally, and possibly providing insight into the pathophysiology of these diseases, analysis of fibroblasts derived from patients with JHF or ISH suggests that CMG2 mutations abrogate normal cell interactions with the extracellular matrix.

Amino Acid Sequence↗
PubMed2003

Novel mutation in the gene encoding c-Abl-binding protein SH3BP2 causes cherubism.

Cherubism is a rare autosomal dominant inherited condition caused by mutations in the c-Abl-binding protein SH3BP2. It is characterized by multiple cystic giant cell lesions of the jaw appearing in early childhood with stabilization and remission after puberty. In the present study, we used direct sequence analysis of the SH3BP2 gene of several individuals from a family with cherubism to search for additional SH3BP2 mutations resulting in cherubism. In affected relatives, we found a previously unreported G to A transition in exon 9 leading to a Gly to Arg substitution at amino acid position 420. G420R has been reported previously with a G to C transversion. To date there have been no disease causing mutations outside exon 9. Therefore, the amino acid sequence from positions 415 to 420 may represent a specific protein domain which, when disrupted, leads to the cherubism phenotype.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Screening of patients with craniosynostosis: molecular strategy.

Craniosynostosis is the premature fusion of calvarial bones leading to an abnormal head shape. The craniosynostosis syndromes are clinically heterogeneous with overlapping features, which make an accurate diagnosis difficult at times. Although the clarification of a genetic lesion does not have a direct impact on patient management in many cases, there is a significant benefit in providing accurate prenatal diagnosis. Genetic counsellors are also able to offer better risk estimates of recurrences to non-manifesting carriers and their extended family members and for affected patients of reproductive age. Advances in gene discovery have shown that craniosynostosis syndromes delineated on clinical bases, with the possible exception of Apert syndrome, are genetically heterogeneous, and mutations have been found in fibroblast growth factor receptors (FGFR) 1, 2, 3 and TWIST. We surveyed 99 craniosynostosis patients at the molecular level and found mutations in 50 of them. Six novel point mutations were identified: three in FGFR2 and three in TWIST. Two Saethre-Chotzen patients with TWIST microdeletions at 7p21 were also found. The other mutations identified have been previously reported. In studying these 99 patients, we developed a diagnostic strategy for craniosynostosis testing, where sequential analysis of recurrent mutations was followed by selective sequencing. This algorithm makes testing of craniosynostosis disorders more efficient and cost-effective.

Craniosynostoses↗
PubMed2003

Clinical and genetic aspects of trigonocephaly: a study of 25 cases.

We reviewed 25 patients ascertained through the finding of trigonocephaly/metopic synostosis as a prominent manifestation. In 16 patients, trigonocephaly/metopic synostosis was the only significant finding (64%); 2 patients had metopic/sagittal synostosis (8%) and in 7 patients the trigonocephaly was part of a syndrome (28%). Among the nonsyndromic cases, 12 were males and 6 were females and the sex ratio was 2 M:1 F. Only one patient with isolated trigonocephaly had an affected parent (5.6%). All nonsyndromic patients had normal psychomotor development. In 2 patients with isolated metopic/sagittal synostosis, FGFR2 and FGFR3 mutations were studied and none were detected. Among the syndromic cases, two had Jacobsen syndrome associated with deletion of chromosome 11q 23 (28.5%). Of the remaining five syndromic cases, different conditions were found including Say-Meyer syndrome, multiple congenital anomalies and bilateral retinoblastoma with no detectable deletion in chromosome 13q14.2 by G-banding chromosomal analysis and FISH, I-cell disease, a new acrocraniofacial dysostosis syndrome, and Opitz C trigonocephaly syndrome. The last two patients were studied for cryptic chromosomal rearrangements, with SKY and subtelomeric FISH probes. Also FGFR2 and FGFR3 mutations were studied in two syndromic cases, but none were found. This study demonstrates that the majority of cases with nonsyndromic trigonocephaly are sporadic and benign, apart from the associated cosmetic implications. Syndromic trigonocephaly cases are causally heterogeneous and associated with chromosomal as well as single gene disorders. An investigation to delineate the underlying cause of trigonocephaly is indicated because of its important implications on medical management for the patient and the reproductive plans for the family.

Abnormalities, Multiple↗
PubMed2002

Teebi hypertelorism syndrome: report of a family with previously unrecognized findings.

We present a family consisting of a mother, a daughter, and a son with Teebi hypertelorism syndrome, including some previously unrecognized manifestations. The clinical findings include a prominent forehead, arched eyebrows, pronounced hypertelorism, long philtrum, mild interdigital webbing, fifth-finger clinodactyly, umbilical anomalies, and hypotonia. The mother and daughter also had ptosis requiring surgical correction. The daughter has bilateral iridochorioretinal colobomas with high hyperopia and a small umbilical hernia. The son has less striking facial features but was born with a small omphalocele, large ASD secundum, PDA, bilateral cryptorchidism right hydronephrosis, and a cystic left kidney. The mother had an umbilical hernia requiring surgical correction as a child and a history of heart murmur. Both children have normal hearing and mild developmental delay. Their high-resolution karyotypes were normal and the FISH for 22q11 microdeletion was negative in the daughter. We conclude that cardiac defects in Teebi hypertelorism syndrome are not rare findings and that eye colobomas and renal anomalies were previously unrecognized.

Abnormalities, Multiple↗
PubMed2002

Frameshift mutation in the cartilage-derived morphogenetic protein 1 (CDMP1) gene and severe acromesomelic chondrodysplasia resembling Grebe-type chondrodysplasia.

Grebe-type chondrodysplasia exhibits a severe form of limb shortening and appendicular bone dysmorphogenesis. Here we report a family with seven males and six females who inherited the disorder in an autosomal recessive fashion. While the carrier parents did not exhibit any apparent skeletal abnormalities, all affected patients had a similar phenotype with unaffected axial and craniofacial bones. Since mutations in the cartilage-derived morphogenetic protein 1 (CDMP1) gene have been reported in similar acromesomelic chondrodysplasias, we examined genomic DNA from affected and normal subjects for possible mutations in CDMP1. In affected subjects, an insertion of a C at nucleotide 297 of the coding sequence was discovered. This insertion produced a shift in the reading frame at amino acid residue 99, causing premature termination of the polypeptide six amino acids downstream. DNA samples from 41 control subjects did not show this mutation. The truncated CDMP1 protein in these subjects is predicted to cause a total loss of its signaling function. The present report confirms that CDMP1 plays an important role in the regulation of axial bone growth during development and suggests that its absence does not impair other developmental processes.

Abnormalities, Multiple↗