Identification of CXorf1, a novel intronless gene in Xq27.3, expressed in human hippocampus

Re-analysis of the Xq27–Xq28 region suggests a weak association of an X-linked gene with sporadic testicular germ cell tumour without cryptorchidism

BACKGROUND

A testicular germ cell tumour (TGCT) predisposing gene has been mapped to the Xq27 region on the X chromosome. These linkage findings remain to be confirmed by other studies.

METHODS

In 276 patients and 169 unaffected first-degree male relatives, 12 microsatellite markers covering the candidate region were genotyped and used to study possible association of TGCT with Xq27.

RESULTS

In contrast to previously reported linkage of familial TGCT and cryptorchidism with Xq27, we observed an association between the subset of TGCT cases without a family history of TGCT or cryptorchism and marker DXS1193 (p=0.014). Carriers of minor alleles were at increased risk (odds ratio (OR) 4.7, confidence interval (CI) 1.1-19.6)

CONCLUSION

We found an association on Xq27 in a subset of TGCT cases, which suggests the presence of an X-linked gene that slightly or moderately increases risk to develop sporadic TGCT but not cryptorchidism.

Autism spectrum disorders associated with X chromosome markers in French-Canadian males

It is now well established that genetic factors play an important role in the pathogenesis of autism disorder and converging lines of evidence suggest the implication of the X chromosome. Using a sample of subjects diagnosed with autism spectrum disorders, exclusively composed of males from French-Canadian (FC) origin, we tested markers covering the entire X chromosome using a family-based association study. Our initial analysis revealed the presence of association at two loci: DXS6789 (P=0.026) and DXS8043 (P=0.0101). In a second step, we added support to the association at DXS8043 using additional markers, additional subjects and a haplotype-based analysis (best obtained P-value=0.00001). These results provide support for the existence of a locus on the X chromosome that predisposes the FC to autism spectrum disorders.

Genomewide scan identifies susceptibility locus for dyslexia on Xq27 in an extended Dutch family

CONTEXT

Dyslexia is a common disorder with a strong genetic component, but despite significant research effort, the aetiology is still largely unknown.

OBJECTIVE

To identify loci contributing to dyslexia risk.

METHODS

This was a genomewide linkage analysis in a single large family. Dutch families with at least two first degree relatives suffering from dyslexia participated in the study. Participants were recruited through an advertisement campaign in papers and magazines. The main outcome measure was linkage between genetic markers and dyslexia phenotype.

RESULTS

Using parametric linkage analysis, we found strong evidence for a locus influencing dyslexia on Xq27.3 (multipoint lod = 3.68). Recombinations in two family members flanked an 8 cM region, comprising 11 currently confirmed genes. All four males carrying the risk haplotype had very low scores on the reading tests. The presentation in females was more variable, but 8/9 females carrying the risk haplotype were diagnosed dyslexic by our composite score, so we considered the putative risk allele to be dominant with reduced penetrance. Linkage was not found in an additional collection of affected sibling pairs.

CONCLUSIONS

A locus influencing dyslexia risk is probably located between markers DXS1227 and DXS8091 on the X chromosome, closely situated to a locus indicated by a published genome scan of English sibling pairs. Although the locus may not be a common cause for dyslexia, the relatively small and gene poor region offers hope to identify the responsible gene.

Identification and characterization of an Xq26-q27 duplication in a family with spina bifida and panhypopituitarism suggests the involvement of two distinct genes

We investigated a family with a duplication, dup(X)q26-q27, that was present in two brothers, their mother, and their maternal grandmother. The brothers carrying the duplication displayed spina bifida and panhypopituitarism, whereas a third healthy brother inherited the normal X chromosome. Preferential inactivation of the X chromosome containing the duplication was evident in healthy carrier females. We determined the boundaries of the Xq26-q27 duplication. Via interphase FISH analysis we narrowed down each of the two breakpoint regions to approximately 300-kb intervals. The proximal breakpoint is located in Xq26.1 between DXS1114 and HPRT and is contained in YAC yWXD599, while the distal breakpoint is located in Xq27.3 between DXS369 and DXS1200 and contained in YAC yWXD758. The duplication comprises about 13 Mb. Evidence from the literature points to a predisposing gene for spina bifida in Xq27. We hypothesize that the spina bifida in the two brothers may be due to interruption of a critical gene in the Xq27 breakpoint region. Several candidate genes were mapped to the Xq27 critical region but none was shown to be disrupted by the duplication event. Recently, M. Lagerström-Fermér et al. (1997, Am. J. Hum. Genet. 60, 910-916) reported on a family with X-linked recessive panhypopituitarism associated with a duplication in Xq26; however, no details were reported on the extent of the duplication. Our study corroborates their hypothesis that X-linked recessive panhypopituitarism is likely to be caused by a gene encoding a dosage-sensitive protein involved in pituitary development. We place the putative gene between DXS1114 and DXS1200, corresponding to the interval defined by the duplication in the present family.

RNAs from all categories generate retrosequences that may be exapted as novel genes or regulatory elements

While the significance of middle repetitive elements had been neglected for a long time, there are again tendencies to ascribe most members of a given middle repetitive sequence family a functional role--as if the discussion of SINE (short interspersed repetitive elements) function only can occupy extreme positions. In this article, I argue that differences between the various classes of retrosequences concern mainly their copy numbers. Consequently, the function of SINEs should be viewed as pragmatic such as, for example, mRNA-derived retrosequences, without underestimating the impact of retroposition for generation of novel protein coding genes or parts thereof (exon shuffling by retroposition) and in particular of SINEs (and retroelements) in modulating genes and their expression. Rapid genomic change by accumulating retrosequences may even facilitate speciation [McDonald, J.F., 1995. Transposable elements: possible catalysts of organismic evolution. Trends Ecol. Evol. 10, 123-126.] In addition to providing mobile regulatory elements, small RNA-derived retrosequences including SINEs can, in analogy to mRNA-derived retrosequences, also give rise to novel small RNA genes. Perhaps not representative for all SINE/master gene relationships, we gained significant knowledge by studying the small neuronal non-messenger RNAs, namely BC1 RNA in rodents and BC200 RNA in primates. BC1 is the first identified master gene generating a subclass of ID repetitive elements, and BC200 is the only known Alu element (monomeric) that was exapted as a novel small RNA encoding gene.