Submitted on November 30, 2006
Accepted on April 16, 2007
Comparative Genomic Analysis of a Mammalian 
- Defensin Gene Cluster
Yashwanth Radhakrishnan1, Mario A Fares2, Frank S. French3, and Susan H Hall3*
1 Reprod Biol, Univ North Carolina
2 Department of Genetics,, University of Dublin, Trinity College, Dublin, Dublin2, Ireland
3 Reprod Biol, Univ North Carolina, United States
* To whom correspondence should be addressed. E-mail: shh{at}med.unc.edu.
Comparative genomic analyses have yielded valuable insights into conserved and divergent aspects of gene function, regulation and evolution. Herein, we describe the characterization of a mouse 
-defensin gene cluster locus on chromosome 2F6. In addition we present the evolutionary analysis of this cluster and its human, rhesus, and rat orthologs. Expression analysis in mouse revealed the occurrence of defensin cluster transcripts in multiple tissues, with the highest abundance in the urogenital tract. Molecular evolutionary analysis suggests that this cluster originated by a series of duplication events, and by positive selection occurring even after the rodent-primate split. In addition the constraints analysis showed higher positive selection in rodents than primates especially distal to the six cysteine array. Positive selection in the evolution of these defensins may relate not only to the evolving enhancement of the ancestral host defense but also to functional innovations in reproduction. The multiplicity of defensins and their preferential over-expression in the urogenital tract indicate that defensins function in the protection and maintenance of fertility.
