Losing maternal care: Neotenic gene expression in the preoptic area of avian brood parasites

Parental care for is critical for offspring survival in many species. However, parental behaviors have been lost in roughly 1% of avian species known as the obligate brood parasites. To shed light on molecular and neurobiological mechanisms mediating brood parasitic behavior, brain gene expression patterns between two brood parasitic species and one closely related non-parasitic Icterid (blackbird) species were compared. Our analyses focused on gene expression changes specifically in the preoptic area (POA), a brain region known to play a critical role in maternal behavior across vertebrates. Using comparative transcriptomic approaches, we identified gene expression patterns associated with brood parasitism and evaluated two alternative explanations for the evolution of brood parasitism: reduced expression of parental-related genes in the POA versus retention of juvenile (neotenic) gene expression. While we did not find evidence for large scale gene downregulation, expression patterns did reflect substantial evidence for neotenic POA gene expression in parasitic birds. Differentially expressed genes with previously established roles in parental care were identified. Targeted examination of these selected candidate genes in additional hypothalamic regions revealed species differences in gene expression patterns is not POA-specific. Together, these results provide new insights into neurogenomics underlying maternal behavior loss in avian brood parasites.