Meeting Abstract
Genomic imprinting, the epigenetically regulated, selective silencing of either maternal or paternal alleles, is essential to embryonic growth and development in mammals. To date, most experimental work on imprinted genes has focused on direct effects of genomic imprinting on conceptus (the collective term for the placenta and fetus) size and embryonic development. However, imprinted genes are highly expressed in placental endocrine cells and are implicated in the induction and maintenance of maternal care. Disruption of genomic imprinting is relatively common in mammalian hybrids: parent-of-origin dependent effects on embryonic growth and development are documented in several rodent genera. We are exploring the effects of placental loss of imprinting on the physiology and maternal behavior of otherwise normal females, using a cross between two closely related species of mice (Mus musculus domesticus and M. spretus). Genomic imprinting is partially disrupted in hybrid conceptuses in this cross; how this may affect maternal behavior and mother-pup interactions is unknown. Pup retrieval, milk letdown and suckling were assayed in the mothers of hybrid and non-hybrid litters, and maternal observations taken over the first nine days post-partum were scored for time in and out of the nest. Pup ultrasonic vocalizations – signals that influence maternal responsiveness – were quantified on days three, six and nine post-partum. As the first test for effects of loss of placental imprinting in a natural system, the results of this experiment will advance understanding of the role of placental imprinted genes in regulating the onset of maternal care and facilitating mother-offspring interactions.
