Vertebral and eye anomalies, cutis aplasia, and short stature (VECS): a new syndrome?

We report on a 6-year-old girl with short stature, facial anomalies, cutis aplasia, nasolacrimal duct obstruction, megalocorneae, kyphoscoliosis with multiple segmentation defects of the thoracic vertebrae, and 11 pairs of ribs. These anomalies together may represent a newly recognized syndrome.

A novel potassium channel gene, KCNQ2, is mutated in an inherited epilepsy of newborns.

Idiopathic generalized epilepsies account for about 40% of epilepsy up to age 40 and commonly have a genetic basis. One type is benign familial neonatal convulsions (BFNC), a dominantly inherited disorder of newborns. We have identified a sub-microscopic deletion of chromosome 20q13.3 that co-segregates with seizures in a BFNC family. Characterization of cDNAs spanning the deleted region identified one encoding a novel voltage-gated potassium channel, KCNQ2, which belongs to a new KQT-like class of potassium channels. Five other BFNC probands were shown to have KCNQ2 mutations, including two transmembrane missense mutations, two frameshifts and one splice-site mutation. This finding in BFNC provides additional evidence that defects in potassium channels are involved in the mammalian epilepsy phenotype.

Linkage analysis of a kindred with inherited 46,XY partial gonadal dysgenesis.

We have reported a kindred in which 46,XY gonadal dysgenesis was inherited in an X-linked (or autosomal dominant sex-limited) manner and in which affected subjects did not have a large duplication of the short arm of the X-chromosome. In the present study we used linkage and sequence analyses to test the role of X-linked and various autosomal genes in the etiology of the familial 46,XY partial gonadal dysgenesis. For analysis of X-linkage, 28 microsatellite polymorphisms and 1 restriction fragment length polymorphism were studied. The genotypes of informative family members were determined at each locus, and data were analyzed. Despite the large number of loci tested, our studies did not establish linkage between the trait and an X-chromosomal locus. With respect to the study of autosomal genes, linkage analysis using a polymorphism within the 3'-untranslated region of the WT1 gene excluded involvement of WT-1 in the etiology of the abnormal gonadal differentiation of the family in this study. Similarly, linkage analysis using four microsatellites on the distal short arm of chromosome 9 was not consistent with linkage. Linkage analysis of a locus close to the SOX9 gene as well as analysis of the coding region of the SOX9 gene suggested that this gene was not associated with the trait in the affected subjects we studied. Our data suggest the role of an autosomal gene in the abnormal gonadal differentiation in the family in the study, but do not formally exclude the role of an X-chromosome gene.

Searching for human epilepsy genes: a progress report.

Application of new genetic techniques has brought remarkable discoveries in the study of genetic diseases. The potential benefits from applying such technology to idiopathic epilepsies include improved understanding of cellular mechanisms and potential new methods of prevention and treatment. The complex problems involved in studying the hereditary epilepsies include: defining of specific phenotypes; detecting genetic and non-genetic heterogeneity; and specifying the appropriate mode of inheritance and penetrance. The gene loci for three primary epilepsies have been localized to specific chromosomal regions, and serve to demonstrate the process used in generalized linkage studies of hereditary epilepsy syndromes. Benign familial neonatal convulsions (BFNC) and Unverricht-Lundborg progressive myoclonus epilepsy are rare single-gene disorders that are sufficiently localized to chromosomal regions that positional cloning studies are likely to succeed. Juvenile myoclonic epilepsy (JME), a common hereditary syndrome with an uncertain mode of inheritance, has been reported to be linked to chromosome 6p. JME presents a challenge for generalized linkage methodology that may be overcome by attending to potential problems reviewed here. The candidate-gene method, combined with studies using animal models, holds promise for understanding these as well as other hereditary epilepsies.

Allelic association and linkage studies in Wilson disease.

We have studied 21 families with Wilson disease (WND), using restriction fragment length polymorphisms (RFLPs) in the 13q14.3 region, to measure linkage of these markers to the disease locus. In addition to previously described markers, we include linkage data for a newly isolated marker (D13S86) and an established marker (D13S56), which were previously not placed on the genetic map in the region of the WND locus. Our data, including those from two recombinant families, support the location of WND between the markers D13S31 and D13S59. We have examined the distribution of marker alleles at the loci studied and have found that D13S31 and D13S228, and associated microsatellite marker, show a non-random distribution on chromosomes carrying the WND mutation. The significant linkage disequilibrium indicates that these two markers must be close to the WND locus.

Seizure characteristics in chromosome 20 benign familial neonatal convulsions.

We studied a kindred of 69 affected individuals with the autosomal dominant epileptic syndrome of benign familial neonatal convulsions, linked to chromosome 20. Forty-two percent had their seizure onset on day 3, while remission took place in 68% during the first 6 weeks. Seizures were brief and the phenotype was of a mixed seizure type, starting with tonic posture, ocular symptoms, apnea, and other autonomic features. The seizure often progressed to clonic movements and motor automatisms. The postictal state was brief, and interictally the neonates looked well. The ictal EEG pattern with generalized suppression of amplitude on onset may be relatively unique. Neurocognitive outcome was usually normal, but the risk for subsequent epilepsy was 16%. Most of the later epilepsy was generalized tonic or tonic-clonic, and some seizures were provoked, raising the possibility of an unusual form of reflex epilepsy.

Report of a kindred with X-linked (or autosomal dominant sex-limited) 46,XY partial gonadal dysgenesis.

The condition termed 46,XY complete gonadal dysgenesis is characterized by the lack of testicular determination with resulting streak gonads, normal Mullerian structures, and female external genitalia. In the partial form, there is incomplete testicular determination with a wide range in the degree of ambiguous genitalia and sexual duct development. We evaluated a kindred in which a partial form of 46,XY gonadal dysgenesis occurred in four subjects from two generations. Pedigree analysis indicated an X-linked or possibly an autosomal sex-limited mode of inheritance. All affected subjects were ascertained because of ambiguous genitalia with minimal virilization. At 10 days of age, the proband had a subnormal plasma level of testosterone, and at 4 months, there was no rise in plasma T after stimulation with hCG. At laparotomy, a dysgenetic gonad was found on the right side, but no gonad was found on the left side. A vas deferens was present on the right, indicating the presence of functional Leydig cells early in fetal life. In the other affected subjects, gonadal tissue was also limited to one side of the abdomen and showed poorly developed seminiferous tubules. The sex-determining region Y gene, which encodes the testis-determining factor, was present and unaltered in the genomic DNA of all affected subjects. Duplication of the distal short arm of the X-chromosome has been associated with 46,XY complete gonadal dysgenesis in some patients. In our studies, Southern blot analysis revealed that sequences of the distal short arm of the X-chromosome (DXS9 to DXS84) were present in single copy, excluding a large duplication in this area of the X. Several kindreds with familial 46,XY complete gonadal dysgenesis have been reported; five of them had evidence of an X-linked mode of inheritance. Our study of a kindred with 46,XY partial gonadal dysgenesis further supports the role of an X chromosome gene in testicular determination. Evidence of some fetal Leydig cell function in the affected subjects of our report suggests that mutations of the putative X-chromosome gene can result in a partial as well as complete defect in testicular determination.

Telangiectasia and optic atrophy in cone-rod degenerations.

The diagnosis of cone-rod dysfunction is made with the electroretinogram (ERG). Characteristically, the photopic ERG is worse than the scotopic ERG, and both are abnormal. Of a larger group of patients with retinal dystrophy, 20 cases of cone-rod dysfunction were identified. All patients had progressive disease, and all three main modes of inheritance were represented. There was remarkable similarity of findings among all patients, including temporal disc atrophy, telangiectasia of disc vessels, and little to no pigmentary retinal changes. Patients were not night-blind unless advanced disease was present. These patients suggest that neither telangiectasia nor temporal optic atrophy is pathognomonic for Leber's optic neuropathy nor dominant optic atrophy, respectively. Using a combination of electrophysiologic testing, fundus changes and modes of inheritance may prove helpful in better classifying the different types of retinal dystrophies, including retinitis pigmentosa.