Comparative physical and transcript maps of approximately 1 Mb around loop-tail, a gene for severe neural tube defects on distal mouse chromosome 1 and human chromosome 1q22-q23.

The homozygous loop-tail (Lp) mouse has a severe neural tube closure defect, analogous to the craniorachischisis phenotype seen in humans. Linkage analysis and physical mapping have previously localized the Lp locus to a region on mouse chromosome 1 defined by the markers D1Mit113-Tagln2. Here we report the construction of sequence-ready bacterial clone contigs encompassing the Lp critical region in both mouse and the orthologous human region (1q22-q23). Twenty-two genes, one EST, and one pseudogene have been identified using a combination of EST database screening, exon amplification, and genomic sequence analysis. The preliminary gene map is Cen-Estm33-AA693056-Ly9-Cd48-Slam-Cd84-Kiaa1215-Nhlh1-Kiaa0253-Copa-Pxf-H326-Pea15-Casq1-Atp1a4-Atp1a2-Estm34-Kcnj9-Kcnj10-Kiaa1355-Tagln2-Nesg1-Crp-Tel. The genes between Slam and Kiaa1355 are positional candidates for Lp. The comparative gene content and order are identical between mouse and human, indicating a high degree of conservation between the two species in this region. Together, the physical and transcript maps described here serve as resources for the identification of the Lp mutation and further define the conservation of this genomic region between mouse and human.