Functional haploinsufficiency of the human homeobox gene MSX2 causes defects in skull ossification.

The genetic analysis of congenital skull malformations provides insight into normal mechanisms of calvarial osteogenesis. Enlarged parietal foramina (PFM) are oval defects of the parietal bones caused by deficient ossification around the parietal notch, which is normally obliterated during the fifth fetal month. PFM are usually asymptomatic, but may be associated with headache, scalp defects and structural or vascular malformations of the brain. Inheritance is frequently autosomal dominant, but no causative mutations have been identified in non-syndromic cases. We describe here heterozygous mutations of the homeobox gene MSX2 (located on 5q34-q35) in three unrelated families with PFM. One is a deletion of approximately 206 kb including the entire gene and the others are intragenic mutations of the DNA-binding homeodomain (RK159-160del and R172H) that predict disruption of critical intramolecular and DNA contacts. Mouse Msx2 protein with either of the homeodomain mutations exhibited more than 85% reduction in binding to an optimal Msx2 DNA-binding site. Our findings contrast with the only described MSX2 homeodomain mutation (P148H), associated with craniosynostosis, that binds with enhanced affinity to the same target. This demonstrates that MSX2 dosage is critical for human skull development and suggests that PFM and craniosynostosis result, respectively, from loss and gain of activity in an MSX2-mediated pathway of calvarial osteogenic differentiation.

Phenotypic variability in 49 cases of ESCO2 mutations, including novel missense and codon deletion in the acetyltransferase domain, correlates with ESCO2 expression and establishes the clinical criteria for Roberts syndrome.

BACKGROUND: Roberts syndrome (RBS) and SC phocomelia are caused by mutations in ESCO2, which codes for an acetyltransferase involved in the regulation of sister chromatid cohesion. Of 26 mutations described to date, only one missense mutation has been reported and all others are predicted to be truncating mutations. Genotype-phenotype analysis has been hampered by limited numbers of patients with clinical information available. OBJECTIVE: To provide unpublished clinical data for 31 patients with proven ESCO2 mutations and combine this series with previously reported clinical and mutation data on 18 cases. Methods Genotype-phenotype correlations and functional effects of two novel ESCO2 mutations were analysed. In situ hybridisation on human embryos at Carnegie stages 14, 17 and 21 was performed to study ESCO2 expression during development. RESULTS AND CONCLUSIONS: Using the cohort of 49 patients, the clinical criteria for RBS were delineated to include: growth retardation; symmetric mesomelic shortening of the limbs in which the upper limbs are more commonly and severely affected than the lower limbs; characteristic facies with microcephaly. The severity of malformations of the facies correlates with the severity of limb reduction. The occurrence of corneal opacities may be associated with specific mutations. Two new mutations, both in the ESCO2 acetyltransferase domain, are described and their acetylation effects in vitro demonstrated. In situ hybridisation on human embryos showed ESCO2 expression in the brain, face, limb, kidney and gonads, which corresponds to the structures affected in RBS.

Clinical and molecular delineation of the 17q21.31 microdeletion syndrome.

BACKGROUND: The chromosome 17q21.31 microdeletion syndrome is a novel genomic disorder that has originally been identified using high resolution genome analyses in patients with unexplained mental retardation. AIM: We report the molecular and/or clinical characterisation of 22 individuals with the 17q21.31 microdeletion syndrome. RESULTS: We estimate the prevalence of the syndrome to be 1 in 16,000 and show that it is highly underdiagnosed. Extensive clinical examination reveals that developmental delay, hypotonia, facial dysmorphisms including a long face, a tubular or pear-shaped nose and a bulbous nasal tip, and a friendly/amiable behaviour are the most characteristic features. Other clinically important features include epilepsy, heart defects and kidney/urologic anomalies. Using high resolution oligonucleotide arrays we narrow the 17q21.31 critical region to a 424 kb genomic segment (chr17: 41046729-41470954, hg17) encompassing at least six genes, among which is the gene encoding microtubule associated protein tau (MAPT). Mutation screening of MAPT in 122 individuals with a phenotype suggestive of 17q21.31 deletion carriers, but who do not carry the recurrent deletion, failed to identify any disease associated variants. In five deletion carriers we identify a <500 bp rearrangement hotspot at the proximal breakpoint contained within an L2 LINE motif and show that in every case examined the parent originating the deletion carries a common 900 kb 17q21.31 inversion polymorphism, indicating that this inversion is a necessary factor for deletion to occur (p<10(-5)). CONCLUSION: Our data establish the 17q21.31 microdeletion syndrome as a clinically and molecularly well recognisable genomic disorder.

Clinical studies on submicroscopic subtelomeric rearrangements: a checklist.

BACKGROUND: Submicroscopic subtelomeric chromosome defects have been found in 7.4% of children with moderate to severe mental retardation and in 0.5% of children with mild retardation. Effective clinical preselection is essential because of the technical complexities and cost of screening for subtelomere deletions. METHODS: We studied 29 patients with a known subtelomeric defect and assessed clinical variables concerning birth history, facial dysmorphism, congenital malformations, and family history. Controls were 110 children with mental retardation of unknown aetiology with normal G banded karyotype and no detectable submicroscopic subtelomeric abnormalities. RESULTS: Prenatal onset of growth retardation was found in 37% compared to 9% of the controls (p<0.0005). A higher percentage of positive family history for mental retardation was reported in the study group than the controls (50% v 21%, p=0.002). Miscarriage(s) were observed in only 8% of the mothers of subtelomeric cases compared to 30% of controls (p=0.028) which was, however, not significant after a Bonferroni correction. Common features (>30%) among subtelomeric deletion cases were microcephaly, short stature, hypertelorism, nasal and ear anomalies, hand anomalies, and cryptorchidism. Two or more facial dysmorphic features were observed in 83% of the subtelomere patients. None of these features was significantly different from the controls. Using the results, a five item checklist was developed which allowed exclusion from further testing in 20% of the mentally retarded children (95% CI 13-28%) in our study without missing any subtelomere cases. As our control group was selected for the "chromosomal phenotype", the specificity of the checklist is likely to be higher in an unselected group of mentally retarded subjects. CONCLUSIONS: Our results suggest that good indicators for subtelomeric defects are prenatal onset of growth retardation and a positive family history for mental retardation. These clinical criteria, in addition to features suggestive of a chromosomal phenotype, resulted in the development of a five item checklist which will improve the diagnostic pick up rate of subtelomeric defects among mentally retarded subjects.

UV-vis spectroscopic study of Co(II)/Co(III) oxidation in poly[M-protoporphyrins] films and their interaction with axial ligands.

A bathochromic shift for both Soret and Q bands in the polyCo(III)PP were indicative of Co(III) oxidation state in film. The presence of an isosbestic point indicates a chemical equilibrium between polyCo(III)PP (band I) in polyCo(III)PP with water as axial neutral ligand (band II). Concentration levels of iodide of 10(-1) M showed irreversible broadening of Soret band with a maximum shift from 400 nm to 380 nm attributed to film reduction. The thiocyanate anion shows a remarkable effect on polyCo(III)PP spectra. The degree of configuration interaction for Q and B transitions is nearly constant in air and water for Ni(II)PP, Cu(II)PP and Zn(II)PP films. The poly[Co(III)-protoporphyrin IX] showed strong deviation from the pattern. This result indicates that the Co atom does not present a planar conformation in polyCo(III)PP which is consistent with the less packed structure of this film. The apparent diffusion coefficients (D') were calculated for electroactive species using the polyNi(II)PP chemically modified electrode, with an experiment short enough to avoid preconcentration. D' was compared with D (diffusion coefficient), obtained with the bare working electrode. Apparent diffusion coefficients (D') changed regularly with molecular volume indicating certain molecular sieving effect.

Autosomal dominant transmission of congenital erythroid hypoplastic anemia with radial abnormalities.

We describe a mother and son with congenital hypoplastic anemia. The mother has apparently normal thumbs and forearms but her son has bilateral radial hypoplasia. They provide a further example of dominant inheritance of Diamond-Blackfan anemia/Aase syndrome and suggest that thumb and radial abnormalities are a component of this syndrome.

A syndrome of mental retardation, short stature, hemolytic anemia, delayed puberty, and abnormal facial appearance: similarities to a report of aldolase A deficiency.

We describe a brother and sister with mental retardation, short stature, delayed puberty, spherocytic anemia, and an abnormal facial appearance. The similarities to a child with aldolase A deficiency are discussed.

Distinctive syndrome of short stature, craniosynostosis, skeletal changes, and malformed ears.

We report on 2 unrelated boys with a distinctive facial appearance of microtia, atretic external auditory meati, small mandible, and microstomia, who also have a skeletal dysplasia, microcephaly, and joint contractures. The skeletal abnormalities, short stature, and microcephaly led to an initial diagnosis of osteodysplastic primordial dwarfism; however, the birth weight of one of the children is not low enough to firmly establish this diagnosis. The similarities were detected by the matching program of the London Dysmorphology Data-base.

Cataracts, motor system disorder, short stature, learning difficulties, and skeletal abnormalities: a new syndrome?

We present a 4-generation family in which affected individuals have cataracts, a motor neuronopathy with upper motor neuron signs, short stature, developmental delay, and skeletal abnormalities. An additional symptom is weakness during pregnancy which resolves after delivery. The condition is inherited in an autosomal dominant manner. The manifestations and inheritance are not found in any previously described conditions. We consider that this is a new syndrome.

Geleophysic dysplasia: a report of three affected boys--prenatal ultrasound does not detect recurrence.

Geleophysic dysplasia is characterized by short stature with short limbs and brachydactyly, a "happy" facial appearance, and joint contractures. Infiltration of heart valves and liver with a mucopolysaccharide-like substance has been demonstrated in some patients. A metabolic pathogenesis is suspected, but has not yet been identified. We report on 3 boys with the condition, 2 of whom are brothers. Serial ultrasound scans were performed on 2 of the cases during pregnancy, but short limbs did not become obvious until after 28 weeks of gestation, making it an uninformative procedure for prenatal diagnosis.

Simpson-Golabi-Behmel syndrome: genotype/phenotype analysis of 18 affected males from 7 unrelated families.

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked overgrowth disorder recently shown to be caused by mutations in the heparan sulfate proteoglycan GPC3 [Pilia et al., Nat Genet; 12:241-247 1996]. We have used Southern blot analysis and polymerase chain reaction amplification of intra-exonic sequences to identify four new GPC3 mutations and further characterize three previously reported SGBS mutations. De novo GPC3 mutations were identified in 2 families. In general, the mutations were unique deletions ranging from less than 0.1 kb to more than 300 kb in length with no evidence of a mutational hot spot discerned. The lack of correlation between the phenotype of 18 affected males from these 7 families and the location and size of the GPC3 gene mutations suggest that SGBS is caused by a nonfunctional GPC3 protein.

Duane's retraction syndrome associated with chromosome 4q27-31 segment deletion.

PURPOSE/METHOD: A 15-year-old boy with bilateral blepharoptosis, bilateral type 1 Duane's retraction syndrome, and mild learning difficulties underwent chromosomal analysis. RESULTS/CONCLUSIONS: A de novo deletion of a segment of the long arm of chromosome 4 (4q27-31) was found. To our knowledge, no other individuals with this chromosome deletion have Duane's retraction syndrome. The chromosome defect lies close to the epidermal growth factor gene, 4q25, which was recently linked to Rieger's syndrome. We suggest that families with Duane's retraction syndrome should be assessed for linkage to the area of 4q27-31.

An improved X-ray spectrometric method for the determination of bromide in whole blood of workers occupationally exposed to methyl bromide.

An X-ray spectrometric method using a sequential wavelength dispersive instrument is described for the analysis of bromide in whole blood from workers occupationally exposed to methyl bromide. The method involves the direct deposition of 100 microL of whole blood onto filter paper discs. Calibration of the instrument is achieved using the standard addition technique for bromide concentrations up to 50 mg/L. Precision studies at concentrations of 6.1, 16.4, and 26.9 mg/L gave relative standard deviation values of 5.8, 4.1, and 2.8%, respectively. The detection limit for the method is 1.2 mg/L.

Transverse limb deficiency, facial clefting and hypoxic renal damage: an association with treatment of maternal hypertension?

Transverse limb defects are reported in a fetus and an infant born to mothers on treatment for hypertension. One pregnancy resulted in an intrauterine death at 20 weeks, and in addition to the limb defects, there was bilateral cleft lip and palate and renal hypoxic damage. It is proposed that the drugs caused maternal hypotension which led to reduced uteroplacental blood flow, fetal hypotension and hypoxia and that the anomalies seen in the two babies are a consequence of these events.

Three infants of diabetic mothers with malformations of left-right asymmetry--further evidence for the aetiological role of diabetes in this malformation spectrum.

We report three babies with malformations of left-right asymmetry who were born to mothers with insulin-dependent diabetes mellitus. One infant had left isomerism and asplenia, one had polysplenia, and the third baby had situs inversus with a neural tube defect. Defects of left-right asymmetry have not previously been well recognized as part of the spectrum of anomalies associated with maternal diabetes. We believe that the association of maternal diabetes with these malformations in the infants is not coincidental, and that diabetes mellitus has an aetiological role in this spectrum of abnormalities. Two of the mothers had elevated HbA1C levels in pregnancy, and thus the malformations may be due to poor glycaemic control, although other teratogenic mechanisms associated with diabetes cannot be excluded. Finally, to our knowledge, the finding of left isomerism with asplenia (part of the spectrum of right isomerism) is rare. The occurrence of both forms of isomerism in different parts of the same body supports the model of random development of laterality following the interruption of normal developmental processes.

Three patients with the osteochondrodysplasia and hypertrichosis syndrome--Cantu syndrome.

Cantu syndrome is a rare condition whose main features are hypertrichosis, cardiac anomalies and wide ribs. Four children have been described and we now present details of a further three. The parents of one of these are first cousins, adding weight to Cantu's theory that the condition is an autosomal recessive disease.