PubMed Health⌕ Search

Biomedical subjects

D Chitayat

Publications and source records attributed to D Chitayat.

At least 55 records · Page 3Linked to original sources
PubMed1999

Heterozygous mutations in the gene encoding noggin affect human joint morphogenesis.

The secreted polypeptide noggin (encoded by the Nog gene) binds and inactivates members of the transforming growth factor beta superfamily of signalling proteins (TGFbeta-FMs), such as BMP4 (ref. 1). By diffusing through extracellular matrices more efficiently than TGFbeta-FMs, noggin may have a principal role in creating morphogenic gradients. During mouse embryogenesis, Nog is expressed at multiple sites, including developing bones. Nog-/- mice die at birth from multiple defects that include bony fusion of the appendicular skeleton. We have identified five dominant human NOG mutations in unrelated families segregating proximal symphalangism (SYM1; OMIM 185800) and a de novo mutation in a patient with unaffected parents. We also found a dominant NOG mutation in a family segregating multiple synostoses syndrome (SYNS1; OMIM 186500); both SYM1 and SYNS1 have multiple joint fusion as their principal feature. All seven NOG mutations alter evolutionarily conserved amino acid residues. The findings reported here confirm that NOG is essential for joint formation and suggest that NOG requirements during skeletogenesis differ between species and between specific skeletal elements within species.

Abnormalities, Multiple↗
PubMed1999

Prenatal detection of cerebral lesions in a fetus with tuberous sclerosis.

We report a newborn, diagnosed prenatally with both cardiac rhabdomyomas and a brain tumor. To the best of our knowledge, this is the first report of central nervous system (CNS) lesions detected prenatally in a child with tuberous sclerosis with term follow-up. At 36 months, the child has normal growth and is developing appropriately. Thus the finding of CNS tumors on fetal ultrasound examination can help in the prenatal diagnosis of tuberous sclerosis but does not necessarily indicate a poor prognosis.

Adult↗
PubMed1999

Brachydactyly type B: clinical description, genetic mapping to chromosome 9q, and evidence for a shared ancestral mutation.

Autosomal dominant brachydactyly type B (BDB) is characterized by nail aplasia with rudimentary or absent distal and middle phalanges. We describe two unrelated families with BDB. One family is English; the other family is Canadian but of English ancestry. We assigned the BDB locus in the Canadian family to an 18-cM interval on 9q, using linkage analysis (LOD score 3.5 at recombination fraction [theta] 0, for marker D9S938). Markers across this interval also cosegregated with the BDB phenotype in the English family (LOD score 2.1 at straight theta=0, for marker D9S277). Within this defined interval is a smaller (7.5-cM) region that contains 10 contiguous markers whose disease-associated haplotype is shared by the two families. This latter result suggests a common founder among families of English descent that are affected with BDB.

Activin Receptors, Type I↗
PubMed1999

CBFA1 mutation analysis and functional correlation with phenotypic variability in cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is a dominantly inherited skeletal dysplasia caused by mutations in the osteoblast-specific transcription factor CBFA1. To correlate CBFA1 mutations in different functional domains with the CCD clinical spectrum, we studied 26 independent cases of CCD and a total of 16 new mutations were identified in 17 families. The majority of mutations were de novo missense mutations that affected conserved residues in the runt domain and completely abolished both DNA binding and transactivation of a reporter gene. These, and mutations which result in premature termination in the runt domain, produced a classic CCD phenotype by abolishing transactivation of the mutant protein with consequent haploinsufficiency. We further identified three putative hypomorphic mutations (R391X, T200A and 90insC) which result in a clinical spectrum including classic and mild CCD, as well as an isolated dental phenotype characterized by delayed eruption of permanent teeth. Functional studies show that two of the three mutations were hypomorphic in nature and two were associated with significant intrafamilial variable expressivity, including isolated dental anomalies without the skeletal features of CCD. Together these data show that variable loss of function due to alterations in the runt and PST domains of CBFA1 may give rise to clinical variability, including classic CCD, mild CCD and isolated primary dental anomalies.

Animals↗
PubMed1998

Familial growth hormone deficiency associated with MRI abnormalities.

Idiopathic growth hormone deficiency is, in most cases, a sporadic condition. In a number of these patients magnetic resonance imaging (MRI) demonstrates a small anterior pituitary, small or absent pituitary stalk, and ectopically located posterior pituitary. These findings have been attributed to a developmental defect, trauma, or ischemia at birth. We report on a case of familial isolated growth hormone deficiency with mother and son demonstrating the MRI findings described above. The son also had a Chiari type I malformation and medial deviation of the carotid arteries secondary to a narrow skull base. Testing failed to identify a mutation in either the Pit-1 gene or GH gene cluster. This case appears to be an autosomal dominant defect in early development, lending support to the hypothesis that dysgenesis, rather than birth trauma, may cause a small anterior pituitary and ectopic posterior pituitary.

Child↗
PubMed1998

Partial tetrasomy with triplication of chromosome (5) (p14-p15.33) in a patient with severe multiple congenital anomalies.

We report on a newborn infant with a de novo triplication of the distal segment of 5p: 46,XX,trp(5) (pter-->p14::p14-->p15.33::p15.33--> qter) and multiple congenital anomalies consistent with triplication of 5p. Partial triplication was documented by fluorescence in situ hybridization with a cosmid probe specific for 5p15.2 and microdissected probes obtained from "5pter." Partial duplication of the short arm of chromosome 5 is associated with a specific phenotype that appears to be dependent on the chromosomal region duplicated. Duplication of 5p with breakpoints proximal to band p14 is generally associated with distinct craniofacial malformations, cardiac, renal, intestinal, and limb defects, and mental retardation, whereas duplications with breakpoints distal to 5p14 result in a milder phenotype characterized by minor facial anomalies, developmental delay, and seizures. The most proximal breakpoints of the partial triplication in this patient was estimated to be 5p14, suggesting that a more severe phenotype can occur with triplication of the more distal segment.

Abnormalities, Multiple↗
PubMed1998

Families with autosomal dominant brachydactyly type E, short stature, and severe hypertension.

BACKGROUND: Rare, monogenic forms of hypertension may give insight into novel mechanisms relevant to essential hypertension. Autosomal dominant hypertension with brachydactyly has been documented in a single Turkish kindred; the gene was mapped to chromosome 12p. OBJECTIVE: To describe the molecular genetics of additional families with autosomal dominant hypertension and brachydactyly. DESIGN: Case series. SETTING: Tertiary care medical centers. PATIENTS: An 11-member Canadian family and a 7-member U.S. family, neither of Turkish background, with autosomal dominant hypertension and type E brachydactyly. MEASUREMENTS: Clinical evaluation, genotyping, and haplotype analyses. RESULTS: The mode of inheritance, the type E brachydactyly, and the propensity for stroke were consistent with autosomal dominant hypertension with brachydactyly. The same markers on chromosome 12p cosegregated with the phenotype in the families. A haplotype analysis strongly supported the conclusion that these families have a molecular defect in the same gene. CONCLUSIONS: The syndrome of autosomal dominant hypertension and brachydactyly is not confined to patients of Turkish origin. All persons with brachydactyly should have their blood pressure measured, and the syndrome should be considered if hypertension is found.

Chromosomes, Human, Pair 12↗
PubMed1998

Clustering of FBN2 mutations in patients with congenital contractural arachnodactyly indicates an important role of the domains encoded by exons 24 through 34 during human development.

Congenital contractural arachnodactyly (CCA) is an autosomal dominant condition phenotypically related to Marfan syndrome (MFS). CCA is caused by mutations in FBN2, whereas MFS results from mutations in FBN1. FBN2 mRNA extracted from 12 unrelated CCA patient cell strains was screened for mutations, and FBN2 mutations were identified in six of these samples. All of the identified FBN2 mutations cluster in a limited region of the gene, a region where mutations in FBN1 produce the severe, congenital form of MFS (so-called neonatal MFS). Furthermore, three of the identified mutations occur in the FBN2 locations exactly corresponding to FBN1 mutations that have been reported in cases of neonatal MFS. These mutations indicate that this central region of both of the fibrillins plays a critical role in human embryogenesis. The limited region of FBN2 that can be mutated to cause CCA may also help to explain the rarity of CCA compared to MFS.

Adult↗
PubMed1998

Prenatally diagnosed neural tube defects: ultrasound, chromosome, and autopsy or postnatal findings in 212 cases.

From January 1990 until December 1996, 212 cases of neural tube defect (NTD) were seen through the Prenatal Diagnosis Program of the University of Toronto. Of the 212 cases, 200 were karyotyped successfully and of these, 13 (6.5%) had chromosome abnormalities. When classified according to the site of the NTD, 2.3% (2/88) of anencephalics, 7.1% (1/14) of encephaloceles, and 10.2% (10/98) of meningomyeloceles had abnormal karyotypes. The absence of associated ultrasound abnormalities was not necessarily predictive of a chromosomally normal fetus; 4/167 (2.4%) of fetuses with isolated NTDs had chromosome abnormalities. Conversely, 24/33 (72%) of fetuses with additional findings on ultrasound had normal chromosomes. The diagnosis of a chromosome abnormality associated with NTD has important implications for recurrence risk and prenatal diagnosis, not only for the parents but potentially for other relatives. Based on our finding that 6.5% of prenatally detected NTDs are associated with chromosome abnormalities, we recommend karyotyping of all fetuses and/or newborns with NTD.

Adolescent↗
PubMed1998

FGFR2 mutation associated with clinical manifestations consistent with Antley-Bixler syndrome.

The Antley-Bixler syndrome (ABS) is a rare syndrome with synostosis of cranial sutures and elbow joints as minimal diagnostic criteria. The inheritance has been suggested to be autosomal recessive based on two families with sib recurrence with both sexes being affected, and two cases born to consanguineous parents. We report the first case of ABS associated with an apparent dominant de novo mutation in the fibroblast growth factor receptor 2 (FGFR2) gene. The patient was found to be heterozygous for a C-->G transversion at nucleotide 1064, which predicts a Ser351Cys amino acid substitution in the IgIII domain of FGFR2. Apart from the craniosynostosis and elbow ankylosis, our patient also presented with severe spinal dysraphism, the first report of such a finding in association with ABS. This suggests that FGFR2 is expressed as early as the fourth week of embryogenesis when somite formation occurs. We propose that the Antley-Bixler syndrome is an autosomal dominant condition with possible gonadal mosaicism. Alternatively, there may be two types of ABS: an autosomal dominant form and an autosomal recessive form. In light of our findings, FGFR mutations should be looked for in other craniosynostosis patients with elbow synostosis.

Abnormalities, Multiple↗
PubMed1998

Normal external genitalia in a female with classical congenital adrenal hyperplasia who was not treated during embryogenesis.

Classical congenital adrenal hyperplasia (CAH) results from an inherited enzymatic defect in cortisol synthesis and more than 90 per cent of cases are due to 21-hydroxylase deficiency. The androgen excess associated with this condition typically results in ambiguous external genitalia in affected females. It has been shown that prenatal treatment with dexamethasone is successful in preventing or reducing genital ambiguity in affected females. Rather than treating with dexamethasone, some couples choose to terminate the pregnancy when an affected fetus is prenatally diagnosed. We report a female with classical CAH who was born with normal external genitalia, although maternal treatment with dexamethasone did not begin until 16 weeks' gestation.

Adrenal Hyperplasia, Congenital↗
PubMed1998

DAX1 mutations map to putative structural domains in a deduced three-dimensional model.

The DAX1 protein is an orphan nuclear hormone receptor based on sequence similarity in the putative ligand-binding domain (LBD). DAX1 mutations result in X-linked adrenal hypoplasia congenita (AHC). Our objective was to identify DAX1 mutations in a series of families, to determine the types of mutations resulting in AHC and to locate single-amino-acid changes in a DAX1 structural model. The 14 new mutations identified among our 17 families with AHC brought the total number of families with AHC to 48 and the number of reported mutations to 42; 1 family showed gonadal mosaicism. These mutations included 23 frameshift, 12 nonsense, and six missense mutations and one single-codon deletion. We mapped the seven single-amino-acid changes to a homology model constructed by use of the three-dimensional crystal structures of the thyroid-hormone receptor and retinoid X receptor alpha. All single-amino-acid changes mapped to the C-terminal half of the DAX1 protein, in the conserved hydrophobic core of the putative LBD, and none affected residues expected to interact directly with a ligand. We conclude that most genetic alterations in DAX1 are frameshift or nonsense mutations and speculate that the codon deletion and missense mutations give insight into the structure and function of DAX1.

Adrenal Glands↗
PubMed1998

Severe classical congenital muscular dystrophy and merosin expression.

It has been suggested that patients with autosomal recessive merosin deficient congenital muscular dystrophy (CMD), as opposed to the merosin positive cases form a homogeneous subgroup of a clinically more severe form of CMD. We examined merosin expression in muscle biopsies from five children with the severe classical form of CMD. Merosin deficiency was found only in 1 patient, a 6-year-old female, with abnormal brain myelination. However, her initial biopsy did not reveal the classical picture of dystrophy. The four merosin positive cases exhibited severe muscle weakness but their brain imagings were normal. There were no familial cases, except for the mother of 1 patient who had a milder form of the disease, suggesting an autosomal dominant mode of inheritance. In contrast to previous reports, the merosin deficient CMD cases were rare in our group. Furthermore, merosin positive cases were also associated with severe phenotype suggesting that a severe phenotype is not exclusive to merosin deficient cases. Finally, the absence of merosin in a neonate with hypotonia and weakness can be helpful in making a definitive diagnosis of CMD, even though the dystrophic process may not be evident yet and histology may be non-specific.

Child↗
PubMed1998

Pedigree analysis of French Canadian families with T14484C Leber's hereditary optic neuropathy.

We analyzed the clinical phenotype and determined the recurrence risks to relatives of patients with T14484C Leber's hereditary optic neuropathy (LHON). LHON is a maternally inherited optic neuropathy that primarily affects adolescent males. It is usually associated with one of three mtDNA mutations: G3460A, G11778A, or T14484C. Definition of recurrence risks for the T14484C mutation previously has not been possible due to the relative scarcity of families with this mutation. We obtained blood samples from index patients and their consenting family members, all of whom were of French Canadian ancestry and screened for LHON mutations in mtDNA. Referring ophthalmologists furnished clinical summaries and patients provided pedigree data. T14484C was the most common mutation in the pedigrees analyzed and was always homoplasmic. In these pedigrees, the ratio of affected males to females was 8:1. Median age at onset for males was 19 years (95th percentile, 40.8 years; range, 6 to 48 years). Some improvement of vision was observed in 58% of patients. Recurrence risks to brothers were 28%, sisters 5%, nephews 30%, nieces 3%, male matrilineal first cousins 19%, and female matrilineal first cousins 4%. Recurrence risks to brothers and nephews were not different; however, recurrence risks to brothers and male cousins and to nephews and male cousins were significantly different. There were no differences in recurrence risks to sisters and nieces or to either group compared with their female cousins. Affected females did not have more affected children than unaffected females. The clinical characteristics of French Canadian patients with T14484C LHON were strikingly similar to those in previous reports, suggesting that recurrence risks are generalizable to other T14484C LHON populations for genetic counseling of T14484C LHON families.

Adolescent↗
PubMed1998

Familial ileal perforation: prenatal diagnosis and postnatal follow-up.

We report sibs (a brother and a sister) who presented prenatally with ultrasound findings of meconium peritonitis and postnatally were found to have perforation of the terminal ileum. The sister presented with fetal ultrasound findings of severe ascites and peritoneal calcifications. She had no prenatal intervention and was born at 38 weeks' gestation. Laparatomy revealed perforation of the terminal ileum with meconium peritonitis. Her post-surgical course was uncomplicated and at 30 months of age her growth and development are normal. Her brother presented prenatally with signs of meconium peritonitis including severe ascites and peritoneal calcifications. Prenatal aspiration of the ascitic fluid was performed and unlike his sister he was born prematurely, was operated on at 8 days, and developed bronchopulmonary dysplasia. He is currently 1 year old and has normal growth and development. The aetiology of the ileal perforation is not known. There were no findings suggesting connective tissue disorder and the aetiology of the intestinal perforation is not known. The occurrence of the same rare abnormality in sibs of different sexes points towards an autosomal recessive disorder.

Adult↗