Lim Homeobox Gene, LHX8, Is Essential for Mouse Oocyte Differentiation and Survival

Lhx8 is a member of the LIM-homeobox transcription factor family and preferentially expressed in oocytes and germ cells within the mouse ovary. We discovered that Lhx8 knockout females lose oocytes within 7 days after birth. At the time of birth, histological examination shows that Lhx8 deficient (Lhx8(-/-)) ovaries are grossly similar to the newborn wild type ovaries. Lhx8(-/-) ovaries fail to maintain the primordial follicles and the transition from primordial to growing follicles does not occur. Lhx8(-/-) ovaries misexpress oocyte-specific genes such as Gdf9, Pou5f1, and Nobox. Very rapid loss of oocytes may partly be due to drastic the down-regulation of Kit and Kitl in Lhx8(-/-) ovaries. We compared Lhx8(-/-) and wild-type ovaries using Affymetrix 430 2.0 microarray platform. Eighty (44%) of 180 of the genes down-regulated more than 5-fold in Lhx8(-/-) ovaries were preferentially expressed in oocytes, whereas only 3 (2%) of 146 genes up-regulated more than 5-fold in the absence of Lhx8 were preferentially expressed in oocytes. In addition, the comparison of genes regulated in Lhx8(-/-) and Nobox(-/-) newborn ovaries discovered a common set of 34 genes whose expression level is affected in both Lhx8 and Nobox deficient mice. Our findings show that Lhx8 is a critical factor for maintenance and differentiation of the oocyte during early oogenesis and it acts in part by down-regulating the Nobox pathway.

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Choi Y, Ballow DJ, Xin Y, Rajkovic A