Genet. Sel. Evol. 37 (2005) S25-S38
DOI: 10.1051/gse:2004029

Physiological effects of major genes affecting ovulation rate in sheep

Kenneth P. McNatty^a, Susan M. Galloway^b, Theresa Wilson^b, Peter Smith^a, Norma L. Hudson^a, Anne O'Connell^a, Adrian H. Bibby^a, Derek A. Heath^a, George H. Davis^c, James P. Hanrahan^d and Jenny L. Juengel<sup>a

a</sup>  AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand
^b  AgResearch, Molecular Biology Unit, Otago University, PO Box 56, Dunedin, New Zealand
^c  AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
^d  Teagasc, Athenry Research Centre, Athenry, Ireland

(Accepted: 26 May 2004 )

Abstract -
Genetic mutations with major effects on ovulation rate in sheep were recently identified in two genes of the transforming growth factor (TGF ) superfamily and a TGF receptor, namely bone morphogenetic protein 15 (BMP15), otherwise known as the growth differentiation factor 9b (GDF9b), GDF9 and activin-like kinase 6 (ALK6) otherwise known as the BMP receptor type IB (BMPRIB). Animals homozygous for the BMP15 or GDF9 mutations are anovulatory whereas animals heterozygous for BMP15 or GDF9 or heterozygous or homozygous for ALK6 have higher than normal ovulation rates. Immunisation of ewes against BMP15 or GDF9 shows that both are essential for normal follicular development and control of ovulation rate. Common features of fertile animals with the BMP15, ALK6 (and possibly GDF9) mutations are changes in oocyte development during early preantral follicular growth, earlier maturation of granulosa cells and ovulation of mature follicles at smaller diameters. In summary, these findings have led to a new paradigm in reproductive biology, namely that the oocyte plays a key role in regulating the ovulation rate.

Key words: genetic mutations / BMP15 / GDF9 / ALK6 / BMPR-IB

Correspondence and reprints: ken.mcnatty@agresearch.co.nz

© INRA, EDP Sciences 2004