A novel SOX9 nonsense mutation, q401x, in a case of campomelic dysplasia with XY sex reversal.

Campomelic dysplasia (CD, MIM 114290) is a rare, often lethal, dominantly inherited, congenital skeletal dysplasia, associated with male-to-female autosomal sex reversal and due to de novo mutations of the SOX9 gene, a tissue-specific transcription factor gene involved both in skeletogenesis and male sexual differentiation. Here we report on a 4 months-old 46,XY sex reversed infant with typical clinical features for CD due to a novel mutation of the SOX9 gene, Q401X, leading to synthesis of a truncated SOX9 protein that completely lacks the C-terminal transactivation domain.

Extended pedigree with multiple cases of XX sex reversal in the absence of SRY and of a mutation at the SOX9 locus.

It is well established that testicular differentiation of the human embryonic gonad depends on the action of the Y-chromosomal gene SRY. However, exceptional cases such as SRY-negative cases of 46,XX testicular disorder of sexual development (DSD), and of 46,XX ovotesticular DSD document that testicular tissue can develop in the absence of the SRY gene. These SRY-negative XX sex reversal cases are very rare and usually sporadic, but a few familial cases have been reported. We present a large, consanguineous family with nine affected individuals with phenotypes ranging from 46,XX testicular DSD to 46,XX ovotesticular DSD, with predominance of male characteristics. Absence of SRY in peripheral blood was documented by fluorescence in situ hybridization (FISH) and PCR analysis in all nine affected individuals, and by FISH analysis on gonadal sections with testicular tissue in four affected individuals. By quantitative PCR, a duplication of the SOX9 gene was excluded. In addition, as linkage analysis showed that the nine affected members of the family do not share a common SOX9 haplotype, any mutation at the SOX9 locus could be ruled out. Together, these findings implicate a mutation at a sex-determining locus other than SRY and SOX9 as the cause for the XX sex reversal trait in this family.

Species-specific evolution of repeated DNA sequences in great apes.

DNA sequencing reveals that the genomes of the human, gorilla and chimpanzee share more than 98% homology. Comparative chromosome painting and gene mapping have demonstrated that only a few rearrangements of a putative ancestral mammalian genome occurred during great ape and human evolution. However, interspecies representational difference analysis (RDA) of the gorilla between human and gorilla revealed gorilla-specific DNA sequences. Cloning and sequencing of gorilla-specific DNA sequences indicate that there are repetitive elements. Gorilla-specific DNA sequences were mapped by fluorescence in-situ hybridization (FISH) to the subcentromeric/centromeric regions of three pairs of gorilla submetacentric chromosomes. These sequences could represent either ancient sequences that got lost in other species, such as human and orang-utan, or, more likely, recent sequences which evolved or originated specifically in the gorilla genome.

Interspecies comparative genome hybridization and interspecies representational difference analysis reveal gross DNA differences between humans and great apes.

Comparative chromosome G-/R-banding, comparative gene mapping and chromosome painting techniques have demonstrated that only few chromosomal rearrangements occurred during great ape and human evolution. Interspecies comparative genome hybridization (CGH), used here in this study, between human, gorilla and pygmy chimpanzee revealed species-specific regions in all three species. In contrast to the human, a far more complex distribution of species-specific blocks was detected with CGH in gorilla and pygmy chimpanzee. Most of these blocks coincide with already described heterochromatic regions on gorilla and chimpanzee chromosomes. Representational difference analysis (RDA) was used to subtract the complex genome of gorilla against human in order to enrich gorilla-specific DNA sequences. Gorilla-specific clones isolated with this technique revealed a 32-bp repeat unit. These clones were mapped by fluorescence in situ hybridization (FISH) to the telomeric regions of gorilla chromosomes that had been shown by interspecies CGH to contain species-specific sequences.

No association between the tyrosine hydroxylase microsatellite marker HUMTH01 and schizophrenia or bipolar I disorder.

Linkage and association studies have implicated the involvement of the tyrosine hydroxylase (TH) gene on chromosome 11p15 in schizophrenia and bipolar disorder (BPD). An association of BPD with a polymorphic tetranucleotide repeat, HUMTH01, located in the first intron of the human TH gene has been reported. Subsequently a rare allele, Ep ([TCAT]10) of this microsatellite marker has been found in French and Tunisian schizophrenic patients only. We have genotyped a different sample of unrelated French schizophrenic and BPD patients from Alsace and matched controls for this polymorphic tetranucleotide repeat sequence. The Ep allele was insignificantly more common in controls than in schizophrenic patients, thus not showing a particular association with schizophrenia. In addition, analysis of the segregation of the Ep allele in the family of one of the schizophrenic patients showed no transmission of this allele from the healthy mother to her schizophrenic daughter. Nevertheless, we did observe a non-significant trend towards an association between HUMTH01 allele D ([TCAT]9) and schizophrenia (Fisher's exact test, p = 0.053). No association was apparent between HUMTH01 and BPD Psychiatr Genet.

Novel and recurrent tyrosine aminotransferase gene mutations in tyrosinemia type II.

Tyrosinemia type II (Richner-Hanhart syndrome, RHS) is a disorder of autosomal recessive inheritance characterized by keratitis, palmoplantar hyperkeratosis, mental retardation, and elevated blood tyrosine levels. The disease results from deficiency in hepatic tyrosine aminotransferase (TAT). We have previously described one deletion and six different point mutations in four RHS patients. We have now analyzed the TAT genes in a further seven unrelated RHS families from Italy, France, the United Kingdom, and the United States. We have established PCR conditions for the amplification of all twelve TAT exons and have screened the products for mutations by direct sequence analysis or by first performing single-strand conformation polymorphism analysis. We have thus identified the presumably pathological mutations in eight RHS alleles, including two nonsense mutations (R57X, E411X) and four amino acid substitutions (R119W, L201R, R433Q, R433W). Only the R57X mutation, which was found in one Scottish and two Italian families, has been previously reported in another Italian family. Haplotype analysis indicates that this mutation, which involves a CpG dinucleotide hot spot, has a common origin in the three Italian families but arose independently in the Scottish family. Two polymorphisms have also been detected, viz., a protein polymorphism, P15S, and a silent substitution S103S (TCG-->TCA). Expression of R433Q and R433W demonstrate reduced activity of the mutant proteins. In all, twelve different TAT gene mutations have now been identified in tyrosinemia type II.

High-resolution mapping of a linkage group on mouse chromosome 8 conserved on human chromosome 16Q.

We have performed a high-resolution linkage analysis for the conserved segment on distal mouse Chromosome (Chr) 8 that is homologous to human Chr 16q. The interspecific backcross used involved M. m. molossinus and an M. m. domesticus line congenic for an M. spretus segment from Chr 8 flanked by phenotypic markers Os (oligosyndactyly) and e, a coat colormarker. From a total of 682 N2 progeny, the 191 animals revealing a recombination event between these phenotypic markers were typed for 23 internal loci. The following locus order with distances in cM was obtained: (centromere)-Os-4.1-Mmp2-0.2-Ces1,Es1, Es22-1.2-Mt1,D8Mit15-2.2-Got2, D8Mit11-3.7-Es30-0.3-Es2, Es7-0.9-Ctra1,Lcat-0.3-Cdh1, Cadp, Nmor1, D8Mit12-0.2-Mov34-2.5-Hp,Tat-0.2-Zfp4-1.6-Zfp1,+ ++Ctrb-10.9-e. In a separate interspecific cross involving 62 meioses, Dpep1 was mapped together with Aprt and Cdh3 at 12.9 cM distal to Hp, Tat, to the vicinity of e. Our data give locus order for markers not previously resolved, add Mmp2 and Dpep1 as new markers on mouse Chr 8, and indicate that Ctra1 is the mouse homolog for human CTRL. Comparison of the order of 17 mouse loci with that of their human homologs reveals that locus order is well conserved and that the conserved segment in the human apparently spans the whole long arm of Chr 16.

Gene mapping on mouse chromosome 8 by interspecific crosses: new data on a linkage group conserved on human chromosome 16q.

A large conserved linkage group exists on mouse chromosome 8 and human chromosome 16q, including the loci for chymotrypsinogen B (Ctrb), haptoglobin (Hp), lecithin:cholesterol acyltransferase (Lcat), metallothionein-1,-2 (Mt-1,-2), tyrosine aminotransferase (Tat), and uvomorulin (Um). Using cloned gene probes, these six loci were mapped in M. m. domesticus X M. spretus interspecific crosses relative to a number of chromosome 8 anchor loci resulting in the gene order Es-1,Es-9-Mt-1,-2-Got-2-Es-2,Es-7,Lcat,Um-Hp,Tat,Ctrb-e. These results complement earlier studies and redefine the conserved segment on mouse chromosome 8, previously defined by the Hp-Tat interval, by the 24-cM interval between Mt-1,-2 and the conserved locus for adenine phosphoribosyltransferase, Aprt, mapped at 25 cM from Es-1 by T. B. Nesterova, P. M. Borodin, S. M. Zakian, and O. L. Serov (1987, Biochem. Genet. 25: 563-568). Within this segment, the gene order appears the same in man and mouse. While map distances between HP-TAT,HP-CTRB, and TAT-CTRB of respectively 7, 11, and 9 cM have previously been measured in man, no crossovers between Hp, Tat, and Ctrb were observed in over 100 meioses in the mouse.

Analysis of two 47,XXX males reveals X-Y interchange and maternal or paternal nondisjunction.

Two cases of 47,XXX males were studied, one of which has been published previously (Bigozzi et al. 1980). Analysis of X-linked restriction fragment length polymorphisms revealed that in this case, one X chromosome was of paternal and two were of maternal origin, whereas in the other case, two X chromosomes were of paternal and one of maternal origin. Southern blot analysis with Y-specific DNA probes demonstrated the presence of Y short arm sequences in both XXX males. In one case, the results obtained pointed to a paracentric inversion on Yp of the patient's father. In situ hybridization indicated that the Y-specific DNA sequences were localized on Xp22.3 in one of the three X chromosomes in both cases. The presence of Y DNA had no effect on random X inactivation. It is concluded that both XXX males originate from aberrant X-Y interchange during paternal meiosis, with coincident nondisjunction of the X chromosome during maternal meiosis in case 1, and during paternal meiosis II in case 2.