Biomedical subjects

Frank H Ruddle

Publications and source records attributed to Frank H Ruddle.

21 records · Page 2Linked to original sources

PubMed2002

Molecular evolution of the HoxA cluster in the three major gnathostome lineages.

The duplication of Hox clusters and their maintenance in a lineage has a prominent but little understood role in chordate evolution. Here we examined how Hox cluster duplication may influence changes in cluster architecture and patterns of noncoding sequence evolution. We sequenced the entire duplicated HoxAa and HoxAb clusters of zebrafish (Danio rerio) and extended the 5' (posterior) part of the HoxM (HoxA-like) cluster of horn shark (Heterodontus francisci) containing the hoxa11 and hoxa13 orthologs as well as intergenic and flanking noncoding sequences. The duplicated HoxA clusters in zebrafish each house considerably fewer genes and are dramatically shorter than the single HoxA clusters of human and horn shark. We compared the intergenic sequences of the HoxA clusters of human, horn shark, zebrafish (Aa, Ab), and striped bass and found extensive conservation of noncoding sequence motifs, i.e., phylogenetic footprints, between the human and horn shark, representing two of the three gnathostome lineages. These are putative cis-regulatory elements that may play a role in the regulation of the ancestral HoxA cluster. In contrast, homologous regions of the duplicated HoxAa and HoxAb clusters of zebrafish and the HoxA cluster of striped bass revealed a striking loss of conservation of these putative cis-regulatory sequences in the 3' (anterior) segment of the cluster, where zebrafish only retains single representatives of group 1, 3, 4, and 5 (HoxAa) and group 2 (HoxAb) genes and in the 5' part of the clusters, where zebrafish retains two copies of the group 13, 11, and 9 genes, i.e., AbdB-like genes. In analyzing patterns of cis-sequence evolution in the 5' part of the clusters, we explicitly looked for evidence of complementary loss of conserved noncoding sequences, as predicted by the duplication-degeneration-complementation model in which genetic redundancy after gene duplication is resolved because of the fixation of complementary degenerative mutations. Our data did not yield evidence supporting this prediction. We conclude that changes in the pattern of cis-sequence conservation after Hox cluster duplication are more consistent with being the outcome of adaptive modification rather than passive mechanisms that erode redundancy created by the duplication event. These results support the view that genome duplications may provide a mechanism whereby master control genes undergo radical modifications conducive to major alterations in body plan. Such genomic revolutions may contribute significantly to the evolutionary process.

Amino Acid Motifs↗

PubMed2002

Genomic structure and functional control of the Dlx3-7 bigene cluster.

The Dlx genes are involved in early vertebrate morphogenesis, notably of the head. The six Dlx genes of mammals are arranged in three convergently transcribed bigene clusters. In this study, we examine the regulation of the Dlx3-7 cluster of the mouse. We obtained and sequenced human and mouse P1 clones covering the entire Dlx3-7 cluster. Comparative analysis of the human and mouse sequences revealed several highly conserved noncoding regions within 30 kb of the Dlx3-7-coding regions. These conserved elements were located both 5' of the coding exons of each gene and in the intergenic region 3' of the exons, suggesting that some enhancers might be shared between genes. We also found that the protein sequence of Dlx7 is evolving more rapidly than that of Dlx3. We conducted a functional study of the 79-kb mouse genomic clone to locate cis-element activity able to reproduce the endogenous expression pattern by using transgenic mice. We inserted a lacZ reporter gene into the first exon of the Dlx3 gene by using homologous recombination in yeast. Strong lacZ expression in embryonic (E) stage E9.5 and E10.5 mouse embryos was found in the limb buds and first and second visceral arches, consistent with the endogenous Dlx3 expression pattern. This result shows that the 79-kb region contains the major cis-elements required to direct the endogenous expression of Dlx3 at stage E10.5. To test for enhancer location, we divided the construct in the mid-intergenic region and injected the Dlx3 gene portion. This shortened fragment lacking Dlx7-flanking sequences is able to drive expression in the limb buds but not in the visceral arches. This observation is consistent with a cis-regulatory enhancer-sharing model within the Dlx bigene cluster.

Animals↗

PubMed2002

Genomic organization of the genes Gtf2ird1, Gtf2i, and Ncf1 at the mouse chromosome 5 region syntenic to the human chromosome 7q11.23 Williams syndrome critical region.

We have recently isolated a mouse ortholog of human GTF2IRD1 that is related to GTF2I. GTF2IRD1 and GTF2I proteins are characterized by the presence of multiple helix-loop-helix domains and a leucine zipper motif. Both paralogs are closely linked and deleted hemizygously in individuals with Williams syndrome, a dominant genetic condition characterized by unique neurocognitive and behavioral features. We have isolated and analyzed the sequence of bacterial artificial chromosome clones from the syntenic mouse chromosome 5 region that contains Gtf2ird1 and Gtf2i as well as a neighboring gene, Ncf1. Gtf2ird1 is composed of 31 exons spanning >100 kb on mouse chromosome 5 and is located between Cyln2 and Gtf2i. Gtf2i is composed of 34 exons spanning about 77 kb. Ncf1, located downstream of Gtf2i, consists of 11 exons that extend over 8 kb. The gene organization of Gtf2ird1, Gtf2i, and Ncf1 is conserved in mice and humans, although the intronic regions are more compact in the mouse genome. The helix-loop-helix repeats of Gtf2ird1 and Gtf2i are encoded separately on adjacent exons and were generated by independent genomic rearrangements. These studies contribute to our knowledge of transcription factor defects and their pathogenesis in haploinsufficiency conditions.

Amino Acid Sequence↗