Epidemiological survey of 214 families with bladder exstrophy-epispadias complex.

PURPOSE: We sought to identify causative nongenetic and genetic risk factors for the bladder exstrophy-epispadias complex. MATERIALS AND METHODS: A total of 237 families with the bladder exstrophy-epispadias complex were invited to participate in the study, and information was obtained from 214 families, mainly from European countries. RESULTS: Two families showed familial occurrence. Male predominance was found among all subgroups comprising epispadias, classic bladder exstrophy and cloacal exstrophy, with male-to-female ratios of 1.4:1, 2.8:1 and 2.0:1, respectively (p = 0.001). No association with parental age, maternal reproductive history or periconceptional maternal exposure to alcohol, drugs, chemical noxae, radiation or infections was found. However, periconceptional maternal exposure to smoking was significantly more common in patients with cloacal exstrophy than in the combined group of patients with epispadias/classic bladder exstrophy (p = 0.009). Only 16.8% of mothers followed the current recommendations of periconceptional folic acid supplementation, and 17.6% had started supplementation before 10 weeks of gestation. Interestingly, in the latter group mothers of patients with cloacal exstrophy were more compliant with folic acid supplementation than were mothers of the combined group of patients with epispadias/classic bladder exstrophy (p = 0.037). Furthermore, mothers of children with cloacal exstrophy knew significantly more often prenatally that their child would have a congenital malformation than did mothers of children with epispadias/classic bladder exstrophy (p <0.0001). CONCLUSIONS: Our study corroborates the hypothesis that epispadias, classic bladder exstrophy and cloacal exstrophy are causally related, representing a spectrum of the same developmental defect, with a small risk of recurrence within families. Embryonic exposure to maternal smoking appears to enforce the severity, whereas periconceptional folic acid supplementation does not seem to alleviate it. There is a disproportional prenatal ultrasound detection rate between severe and mild phenotypes, possibly due to the neglect of imaging of full bladders with a focus on neural tube defects.

Genetic analysis of non-syndromic craniosynostosis.

Craniosynostosis is a common malformation occurring in 3-5 per 10,000 live births. Most often craniosynostosis occurs as an isolated (i.e. non-syndromic) anomaly. Non-syndromic craniosynostosis (NSC) is a clinically and genetically heterogeneous condition that has the characteristics of a multifactorial trait. It is believed that each sutural synostosis (e.g. sagittal, coronal) represents a different disease. Significant progress has been made in understanding the clinical and molecular aspects of monogenic syndromic craniosynostosis. However, the phenotypic characterization of NSC is incomplete and its causes remain unknown. This review summarizes the available knowledge on NSC and presents a systematic approach aimed at the identification of genetic and non-genetic factors contributing to the risk of this common craniofacial defect.

Analysis of candidate genes on chromosome 2 in oral cleft case-parent trios from three populations.

Isolated oral clefts, including cleft lip with/without cleft palate (CL/P) and cleft palate (CP), have a complex and heterogeneous etiology. Case-parent trios from three populations were used to study genes spanning chromosome 2, where single nucleotide polymorphic (SNP) markers were analyzed individually and as haplotypes. Case-parent trios from three populations (74 from Maryland, 64 from Singapore and 95 from Taiwan) were genotyped for 962 SNPs in 104 genes on chromosome 2, including two well-recognized candidate genes: TGFA and SATB2. Individual SNPs and haplotypes (in sliding windows of 2-5 SNPs) were used to test for linkage and disequilibrium separately in CL/P and CP trios. A novel candidate gene (ZNF533) showed consistent evidence of linkage and disequilibrium in all three populations for both CL/P and CP. SNPs in key regions of ZNF533 showed considerable variability in estimated genotypic odds ratios and their significance, suggesting allelic heterogeneity. Haplotype frequencies for regions of ZNF533 were estimated and used to partition genetic variance into among-and within-population components. Wright's fixation index, a measure of genetic diversity, showed little difference between Singapore and Taiwan compared with Maryland. The tensin-1 gene (TNS1) also showed evidence of linkage and disequilibrium among both CL/P and CP trios in all three populations, albeit at a lower level of significance. Additional genes (VAX2, GLI2, ZHFX1B on 2p; WNT6-WNT10A and COL4A3-COL4A4 on 2q) showed consistent evidence of linkage and disequilibrium only among CL/P trios in all three populations, and TGFA showed significant evidence in two of three populations.

Molecular screening for microdeletions at 9p22-p24 and 11q23-q24 in a large cohort of patients with trigonocephaly.

Trigonocephaly is a rare form of craniosynostosis characterized by the premature closure of the metopic suture. To contribute to a better understanding of the genetic basis of metopic synostosis and in an attempt to restrict the candidate regions related to metopic suture fusion, we studied 76 unrelated patients with syndromic and non-syndromic trigonocephaly. We found a larger proportion of syndromic cases in our population and the ratio of affected male to female was 1.8 : 1 and 5 : 1 in the non-syndromic and syndromic groups, respectively. A microdeletion screening at 9p22-p24 and 11q23-q24 was carried out for all patients and deletions in seven of them were detected, corresponding to 19.4% of all syndromic cases. Deletions were not found in non-syndromic patients. We suggest that a molecular screening for microdeletions at 9p22-p24 and 11q23-q24 should be offered to all syndromic cases with an apparently normal karyotype because it can potentially elucidate the cause of trigonocephaly in this subset of patients. We also suggest that genes on the X-chromosome play a major role in syndromic trigonocephaly.

The relationship of plasma glutamine to ammonium and of glycine to acid-base balance in propionic acidaemia.

Hyperammonaemia is a common and serious complication of propionic acidaemia. Treatment of hyperammonaemia with sodium phenylacetate or phenylbutyrate has not been well studied in this disorder. We reviewed the medical records of 5 patients with propionic acidaemia over a 16-year period. We collected information on events where plasma amino acids and ammonium, plasma acids and acid-base balance, or all 3 parameters were obtained simultaneously. All patients were on protein-restricted diet and carnitine throughout the period. In contrast to hyperammonaemia in patients with a urea cycle disorder, plasma glutamine levels were below the normal mean and there was no correlation between plasma ammonium and glutamine levels. The absence of positive correlation between plasma glutamine and ammonium suggests that the routine use of sodium phenylacetate or phenylbutyrate to treat hyperammonaemia in propionic acidaemia should be questioned until further studies are done. Throughout follow-up of our propionic acidaemia patients, we have observed that plasma glycine levels correlated positively with serum bicarbonate. The association of high plasma glycine with good acid-base balance might have a potential role in management and warrants further investigation.

Physical map of the chromosome 6q22 region containing the oculodentodigital dysplasia locus: analysis of thirteen candidate genes and identification of novel ESTs and DNA polymorphisms.

Oculodentodigital dysplasia (ODDD) is an autosomal dominant condition with congenital anomalies of the craniofacial and limb regions and neurodegeneration. Genetic anticipation for the dysmorphic and neurologic features has been inferred in a few families. Our previous linkage studies have refined the ODDD candidate region to chromosome 6q22-->q23. In an attempt to clone the ODDD gene, we created a yeast artificial chromosome contig with 31 redundant clones spanning the region and identified and ordered candidate genes and markers. Fluorescent IN SITU hybridization mapped two of these YAC clones to chromosome 6q22.2 telomeric to a known 6q21 fragile site, excluding it as a possible cause of the suggested anticipation. We performed mutation analysis on thirteen candidate genes - GRIK2, HDAC2, COL10A1, PTD013, KPNA5, PIST, ROS1, BRD7, PLN, HSF2, PKIB, FABP7, and HEY2. Although no mutations were found, we identified 44 polymorphisms, including 28 single nucleotide polymorphisms. Direct cDNA selection was performed and fifty-five clones were found to contain sequences that were not previously reported as known genes or ESTs. These clones and polymorphisms will assist in the further characterization of this region and identification of disease genes.

Online Mendelian Inheritance in Man (OMIM) as a knowledgebase for human developmental disorders.

In this review, we summarize the current genetic information on human developmental disorders found in Online Mendelian Inheritance in Man (OMIM). The OMIM catalogues human phenotypes and genotypes and relevant mouse models. Among the more than 11005 genetic disorders and loci, we found at least 1231 human conditions with known gene mutationsffWe searched for human developmental disorders that present with structural defects during the perinatal period, and identified 162 such entries. We classified these entries by phenotypic features (e.g., skeletal dysplasias, axis and laterality defects, or eye disorders) and by the type of gene mutated (e.g., genes coding for transcription factors, structural proteins, enzymes, or receptors). Thirty-eight entries have allelic variants with gene mutations causing different functional consequences, thereby altering their interactions with modifying genes. Thirty-two entries show genetic heterogeneity due to either functional redundancy of more than one gene or genes that interact in common developmental pathways. Although many different types of genes are mutated in developmental disorders, we found that the disease genes are transcription factors in 49 entries. Mouse models are available for many of the human conditions, with the majority of these mutants being secondary to null mutations. These data allow us to begin to elucidate the complex developmental pathways involved in the molecular pathogenesis of human malformations.

Three cases of intravenous sodium benzoate and sodium phenylacetate toxicity occurring in the treatment of acute hyperammonaemia.

Intravenous sodium benzoate and sodium phenylacetate have been used successfully in the treatment of acute hyperammonaemia in patients with urea cycle disorders. They provide alternative pathways for waste nitrogen disposal and help maintain nitrogen homeostasis. However, we report three patients with hyperammonaemia who received inappropriate doses of intravenous sodium benzoate and sodium phenylacetate that resulted in severe complications. Ambiguous medical prescriptions and inadequate cross-checking of drug dosage by physicians, nurses and pharmacists were the main causes of these incidents. All the patients presented with alteration in mental status, Kussmaul respiration and a partially compensated metabolic acidosis with an increased anion gap. Two patients developed cerebral oedema and hypotension and died. The third survived after haemodialysis. Plasma levels of benzoate and phenylacetate were excessively high. The possible mechanisms of toxicity, management and safety measures are discussed.

Paternal origin of FGFR2 mutations in sporadic cases of Crouzon syndrome and Pfeiffer syndrome.

Crouzon syndrome and Pfeiffer syndrome are both autosomal dominant craniosynostotic disorders that can be caused by mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. To determine the parental origin of these FGFR2 mutations, the amplification refractory mutation system (ARMS) was used. ARMS PCR primers were developed to recognize polymorphisms that could distinguish maternal and paternal alleles. A total of 4,374 bases between introns IIIa and 11 of the FGFR2 gene were sequenced and were assayed by heteroduplex analysis, to identify polymorphisms. Two polymorphisms (1333TA/TATA and 2710 C/T) were found and were used with two previously described polymorphisms, to screen a total of 41 families. Twenty-two of these families were shown to be informative (11 for Crouzon syndrome and 11 for Pfeiffer syndrome). Eleven different mutations in the 22 families were detected by either restriction digest or allele-specific oligonucleotide hybridization of ARMS PCR products. We molecularly proved the origin of these different mutations to be paternal for all informative cases analyzed (P=2. 4x10-7; 95% confidence limits 87%-100%). Advanced paternal age was noted for the fathers of patients with Crouzon syndrome or Pfeiffer syndrome, compared with the fathers of control individuals (34. 50+/-7.65 years vs. 30.45+/-1.28 years, P<.01). Our data on advanced paternal age corroborates and extends previous clinical evidence based on statistical analyses as well as additional reports of advanced paternal age associated with paternal origin of three sporadic mutations causing Apert syndrome (FGFR2) and achondroplasia (FGFR3). Our results suggest that older men either have accumulated or are more susceptible to a variety of germline mutations.

Linkage analysis narrows the critical region for oculodentodigital dysplasia to chromosome 6q22-q23.

Oculodentodigital dysplasia (ODDD) is an autosomal dominant condition with high penetrance and variable expressivity. The anomalies of the craniofacial region, eyes, teeth, and limbs indicate abnormal morphogenesis during early fetal development. Neurologic abnormalities occur later in life and appear to be secondary to white matter degeneration and basal ganglia changes. In familial cases, the dysmorphic and/or neurodegenerative components of the phenotype can be more severe and/or present at a younger age in subsequent generations, suggesting genetic anticipation. These clinical features suggest that the ODDD gene is pleiotropic with important functions throughout pre- and postnatal development. We have performed two-point linkage analysis with seven ODDD families and 19 microsatellite markers on chromosome 6q spanning a genetic distance of approximately 11 cM in males and 20 cM in females. We have refined the location of the ODDD gene between DNA markers D6S266/D6S261 (centromeric) and D6S1639 (telomeric), an interval of 1.01 (male) to 2.87 (female) cM. The strongest linkage was to DNA marker D6S433 (Zmax = 8.96, thetamax = 0.001). Families show significant linkage to chromosome 6q22-q23 and no evidence for genetic heterogeneity.

A unique point mutation in the PMP22 gene is associated with Charcot-Marie-Tooth disease and deafness.

Charcot-Marie-Tooth disease (CMT) with deafness is clinically distinct among the genetically heterogeneous group of CMT disorders. Molecular studies in a large family with autosomal dominant CMT and deafness have not been reported. The present molecular study involves a family with progressive features of CMT and deafness, originally reported by Kousseff et al. Genetic analysis of 70 individuals (31 affected, 28 unaffected, and 11 spouses) revealed linkage to markers on chromosome 17p11.2-p12, with a maximum LOD score of 9.01 for marker D17S1357 at a recombination fraction of .03. Haplotype analysis placed the CMT-deafness locus between markers D17S839 and D17S122, a approximately 0.6-Mb interval. This critical region lies within the CMT type 1A duplication region and excludes MYO15, a gene coding an unconventional myosin that causes a form of autosomal recessive deafness called DFNB3. Affected individuals from this family do not have the common 1.5-Mb duplication of CMT type 1A. Direct sequencing of the candidate peripheral myelin protein 22 (PMP22) gene detected a unique G-->C transversion in the heterozygous state in all affected individuals, at position 248 in coding exon 3, predicted to result in an Ala67Pro substitution in the second transmembrane domain of PMP22.

Familial craniosynostosis, anal anomalies, and porokeratosis: CAP syndrome.

We report on the occurrence of coronal craniosynostosis, anal anomalies, and porokeratosis in two male sibs. A third male sib was phenotypically normal as were the parents. The occurrence of these three clinical features has, to our knowledge, not been reported before. Cutaneous or anal anomalies or both have been reported in a number of syndromes associated with craniosynostosis, including Crouzon, Pfeiffer, Apert, and Beare-Stevenson syndromes. These syndromes are associated with mutations in the fibroblast growth factor receptor genes FGFR1, FGFR2, and FGFR3. They are inherited in an autosomal dominant fashion. In contrast, the cases we report do not carry any of the common FGFR mutations and the pedigree suggests autosomal or X linked recessive inheritance.

High frequency in vivo loss of heterozygosity is primarily a consequence of mitotic recombination.

We have used the adenine phosphoribosyltransferase gene (APRT; 16q24) to investigate the mechanisms of loss of heterozygosity (LOH) in normal human somatic cells in vivo. APRT-deficient (APRT-/-, APRT-/0) T lymphocytes from the peripheral blood of four obligate APRT heterozygotes (APRT+/-) with characterized germ-line mutations were selected in medium containing 100 microM 2,6-diaminopurine. A total of 80 2,6-diaminopurine-resistant T-cell clones from 2 of the heterozygotes were analyzed for this study. The presence or absence of LOH of proximal linked microsatellite repeat markers was used to divide the clones into two groups: (a) those in which LOH was likely due to localized changes in APRT (e.g., point mutations); and (b) those with LOH at additional loci. A total of 61 clones (76%) exhibited LOH of linked microsatellite repeat markers at different locations on 16q, which extended from the smallest measured region (<5.5 cM) to the entire 16q arm. The remaining 19 clones (24%) had point mutations in APRT or other relatively minor alterations. Ten clones with LOH encompassing different regions of 16q were examined by conventional cytogenetics and by fluorescence in situ hybridization using an APRT cosmid probe. All clones exhibited a normal diploid karyotype, and nine exhibited two copies of APRT. The one clone that was hemizygous for APRT had the smallest observed region of LOH in clones from that individual. These results indicate that mitotic recombination and, to a much lesser extent, deletion may be the primary mechanisms for the relatively high frequency of in vivo LOH observed in normal human T cells. Because LOH leads to the expression of recessive tumor suppressor genes in many cancers, these data have significant implications for the role of LOH in the early stages of tumor development, especially in breast cancer.

Adult-onset neurodegenerative disorder due to proteolipid protein gene mutation in the mother of a man with Pelizaeus-Merzbacher disease.

A 23-year-old man with Pelizaeus-Merzbacher disease had a novel mutation, C344A (Thr115Lys), in exon 3 of the proteolipid protein gene (PLP) His mother, heterozygous for the mutation, developed progressive personality change and a gait disorder in her mid-20s. Her MRI at age 53 showed a diffuse severe leukodystrophy. This report extends the phenotypic range of disease due to PLP gene mutations to include adult-onset dementia in females.

Pelizaeus-Merzbacher disease caused by a de novo mutation that originated in exon 2 of the maternal great-grandfather of the propositus.

Pelizaeus-Merzbacher disease (PMD) is an X-linked dysmyelinating disorder of the central nervous system. Many cases of PMD can be attributed to defects in the proteolipid protein gene (PLP). To date, with one exception, each family has had either no or a unique mutation in one of the seven exons of PLP. We describe a new missense mutation in exon 2 of the PLP gene of an affected individual. This mutation codes for Ile instead of Thr at codon 42. The point mutation originated in the X chromosome of the maternal great-grandfather of the propositus. This was determined from the pattern of inheritance of the AhaII polymorphism and a series of microsatellite markers that are localized near PLP at Xq22.

Pelizaeus-Merzbacher disease in a family of Portuguese origin caused by a point mutation in exon 5 of the proteolipid protein gene.

Single-strand conformational polymorphism analysis of an affected male with Pelizaeus-Merzbacher disease (PMD) showed a slight change in mobility of amplified exon 5 of the proteolipid protein (PLP) gene. The exon was sequenced and a G-->A transition at codon 216 was found. This mutation eliminates a BstNI restriction site and creates a MaeI restriction site. In 1989, Gencic et al. reported a mutation that destroyed the same BstNI site, but resulted in a substitution at codon 215 [Am J Hum Genet 45:435-442]. The mutation we report here is also present in the patient's mother and her male fetus as determined by polymerase chain reaction analysis of amniocytes.