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Interpretive Summary: Gene expression in the amygdala and hippocampus of cyclic and acyclic gilts

By: Dr. Emily Taylor

Reproductive failure affects up to 30% of replacement gilts, causing a massive reduction in profitability for a producer. More specifically, there are two types of prebreeding anestrus that cause reproductive failure, including the delay in attaining puberty (prepubertal anestrus, PPA) or silent ovulation (behavioral anestrus, BA). The amygdala and hippocampus (neural tissues) play a significant role in regulating sexual behavior, social interactions, and receptivity to males. The authors' goal was to gain a functional understanding of how these rarely studied tissues may differ between pubertal phenotypes and different stages of the estrous cycle of gilts. Gene expression of the amygdala and hippocampus of gilts were analyzed in three comparisons:

  1. PPA cases and cyclic controls at the follicular phase of the estrous cycle

  2. BA cases and cyclic controls at the luteal phase of the estrous cycle

  3. Gilts at different stages of the ovarian cycle 

As a result, data proved that differently expressed genes (DEG) between PPA and BA cases and their respective cyclic controls were involved in neurological and behavioral disorders. In addition, they also found involvement of nervous system functions that could, directly and indirectly, affect the development of behaviors related to estrus. The most significant number of DEGs in the hippocampus and amygdala were found in the comparison between gilts in the follicular vs. luteal phase. These DEGs were found to be involved in adult neurogenesis and neural synapse. Authors suggest that these tissues undergo structural changes and synaptic plasticity in gilts during the respective cyclic phases. 

This study is the first to associate the estrous cycle stage with dynamic changes in gene expression within the hippocampus and amygdala. These results indicate that gonadal steroids play a role in regulating the biology of these tissues. Authors believe these data are essential for developing new hypotheses and guiding future studies. 

This article is available in the Journal of Animal Science.