Other neuroactive genes with roles in appetite and fat regulation in adult life – IRX3, IRX5, NHLH2 – were also highly expressed; IRX3 and IRX5 have postulated roles in obesity regulation as well as ovary folliculogenesis50–52,] and mice require Nhlh2 for meiosis and fertility as well as for energy metabolism53. Here, IRX5 is linked to obesity due to melanocortin 4 receptor deficiency.