CpG islands of chicken are concentrated on microchromosomes.
The chicken karyotype comprises 39 chromosome pairs of which at least 29 are 'microchromosomes'. Microchromosomes account for about 25% of the genomic DNA, but they are cytologically indistinguishable from one another (1). Due to technical limitations there is a strong bias of mapped genes within the chicken genome database ChickGBASE (2) towards macrochromosomes 1-6 and Z, with specific assignments to only one microchromosome (3,4). Several genes have, however, been assigned to the microchromosome group as a whole (3,5-9), demonstrating that these tiny chromosomes do not represent genetically inert DNA. To determine the overall chromosomal distribution of genes, as well as to provide a mapping resource, we prepared a CpG island library from chicken using differential binding to a methyl-CpG chicken using differential binding to a methyl-CpG binding column before and after de novo methylation (10). Surprisingly, we found that chicken CpG islands are highly concentrated on the microchromosomes, whereas macrochromosomes 1-6 are comparatively gene-poor by this assay. Our results raise the possibility that gene density on chicken microchromosomes approaches the maximum value known for vertebrates.
McQueen
H A
HA
Institute of Cell and Molecular Biology, University of Edinburgh, Scotland.
Fantes
J
J
Cross
S H
SH
Clark
V H
VH
Archibald
A L
AL
Bird
A P
AP
D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D002874:Chromosome Mapping; D018899:CpG Islands / Q000235:genetics*; D004247:DNA; D015723:Gene Library; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data
D004247:DNA