Mapping of leptin and its syntenic genes to chicken chromosome 1p

A radiation hybrid panel of chicken - hamster Wg3hCl2 cells, was used to map the genome location of the chicken leptin gene. Contrary to our expectations based on comparative genome mapping and sequence characteristics, the chicken leptin was not located on a microchromosome, which are known to contain GC-rich and repetitive regions, but at the distal tip of the largest chromosome (1p). Following conserved synteny with other vertebrates, we also mapped five additional genes to this genomic region (ARF5, SND1, LRRC4, RBM28, and FLNC), bridging the genomic gap in the current Galgal5 build for this chromosome region. All of the short scaffolds containing these genes were found to consist of GC-rich (54 to 65%) sequences comparing to the average GC-content of 40% on chromosome 1. In this syntenic group, the RNA-binding protein 28 (RBM28) was in the closest proximity to leptin. We deduced the full-length of the RBM28 cDNA sequence and profiled its expression patterns detecting a negative correlation (R = -0.7) between the expression of leptin and of RBM28 across tissues expressing at least one of the genes above average level. This suggested a local regulatory interaction between these genes. In adipose tissues, we observed significant increase in RBM28 mRNA expression in breeds with lean phenotypes raising the possibility that this regulation is related to the control of the energy balance.