Assignment of the human homeobox 11-like 2 gene (HOX11L2) to chromosome 5q34-->q35 by radiation hybrid mapping

Nuclear factor Y drives basal transcription of the human TLX3, a gene overexpressed in T-cell acute lymphocytic leukemia

Based on a knocked-out mouse model and a few expression studies, TLX3 is regarded as a homeobox gene crucial for the development of the autonomic nervous system. This gene can undergo rearrangements or deregulation, giving rise to T-cell acute lymphocytic leukemia. The present report is focused on the identification of elements and factors playing a role in the TLX3 physiologic expression regulation and therefore likely to be involved in cancer development. In particular, after identifying the transcription start points, we have made use of in vitro transfection assays to show that the 5'-untranslated region of the gene is necessary for the basal promoter activity in cell lines from different origin. By site-directed mutagenesis, two tandem CCAAT boxes have been localized as critical elements of this region. In vivo chromatin immunoprecipitation and electrophoretic mobility shift assays have indicated that nuclear factor Y (NFY) recognizes these sites in all the analyzed cell lines. The physiologic role of such an interaction has been confirmed by a dominant-negative version of the NFY transcription factor that has turned out to decrease both in vitro TLX3 promoter activity and endogenous amount of mRNA. Finally, a consistent in vivo TLX3 expression impairment was also achieved after NFY mRNA knockdown. The full characterization of the TLX3 transcription regulation will ultimately provide crucial elements to define the involvement of this gene in T-cell acute lymphocytic leukemia development.

Mutational analysis of the RNX gene in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is a rare syndrome characterized by failure of autonomic respiratory control, often presenting with other dysfunctions of the autonomic nervous system. Segregation analysis suggested a complex model of inheritance with a major locus involved. Disruption of the Rnx gene, a member of the Hox11 family of homeobox genes, in embryonic stem cells produced mice showing a phenotype similar to CCHS. Based on this observation, we have carried out mutation screening of the RNX gene in a set of 13 patients affected with CCHS, 2 of whom showing association with Hirschsprung disease. Single-strand conformational polymorphism analysis and direct sequencing of the whole coding portion of the RNX gene and of 1,311 bp of 5' flanking region were performed. No sequence variant was identified, with the exception of a private nucleotide change at position -874 bp from the ATG codon in two siblings affected with isolated CCHS. A functional test, performed by using the luciferase gene reporter system, has not shown any significant difference in the activity of the promoter region carrying this latter nucleotide change with respect to the wild-type allele. We conclude that RNX, and presumably its expression, are not altered in our index cases of CCHS.

Molecular cloning and developmental expression of Tlx (Hox11) genes in zebrafish (Danio rerio)

Tlx (Hox11) genes are orphan homeobox genes that play critical roles in the regulation of early developmental processes in vertebrates. Here, we report the identification and expression patterns of three members of the zebrafish Tlx family. These genes share similar, but not identical, expression patterns with other vertebrate Tlx-1 and Tlx-3 genes. Tlx-1 is expressed early in the developing hindbrain and pharyngeal arches, and later in the putative splenic primordium. However, unlike its orthologues, zebrafish Tlx-1 is not expressed in the cranial sensory ganglia or spinal cord. Two homologues of Tlx-3 were identified: Tlx-3a and Tlx-3b, which are both expressed in discrete regions of the developing nervous system, including the cranial sensory ganglia and Rohon-Beard neurons. However, only Tlx-3a is expressed in the statoacoustic cranial ganglia, enteric neurons and non-neural tissues such as the fin bud and pharyngeal arches and Tlx-3b is only expressed in the dorsal root ganglia.