First Gene on the Avian W Chromosome (CHD) Provides a Tag for Universal Sexing of Non-Ratite Birds

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 263; no. 1377; pp. 1635 - 1641
• Main Author: Ellergren, Hans
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22-12-1996
• Subjects: Animals; Avian Proteins; Base Sequence; Birds; Birds - genetics; Chickens; Chickens - genetics; Cloning, Molecular; DNA; DNA Primers - genetics; DNA-Binding Proteins - genetics; Female; Female animals; Genes; Genomics; Male; Male animals; Mice; Molecular Sequence Data; Polymerase Chain Reaction; Polymorphism, Restriction Fragment Length; Sex chromosomes; Sex Chromosomes - genetics; Sex Determination Analysis - methods; Species Specificity; W chromosome
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.1996.0239

The avian W chromosome shares many features with the mammalian Y chromosome: it is small, mostly heterochromatic, and filled with large repetitive arrays. No gene has so far been assigned to the W chromosome in any bird species and, as a practical consequence, a general tag for avian gender identification on the molecular level is lacking. Here I describe the isolation of a chicken homologue to the mouse chromo-helicase-DNA binding (CHD) gene which encodes a protein involved in global regulation of transcriptional activation on the chromatin level. The avian CHD gene exists in two genomic copies, one of which (termed CHD-W) was located on the W chromosome in all non-ratite species investigated. The gene displays extreme levels of sequence conservation since chicken CHD-W and mouse CHD are 82.9% and 95.6% identical at the nucleotide and amino acid level respectively. Molecular sexing can be accomplished in probably all non-ratite birds by hybridizing Southern blots with CHD probes. PCR-based gender identification is also demonstrated. A general system for avian sexing should facilitate many studies of behaviour, evolutionary ecology, genetics, and evolution.