Sex differences in cell migration in the preoptic area/anterior hypothalamus of mice

The preoptic area/anterior hypothalamus (POA/AH) sits as a boundary region rostral to the classical diencephalic hypothalamus and ventral to the telen cephalic septal region. Numerous studies have pointed to the region's impor tance for sex-dependent functions. Previous studies suggested that migrator y guidance cues within this region might be particularly unique in their di versity. To better understand the early development and differentiation of the POA/AH, cytoarchitectural, birthdate, immunocytochemical, and cell migr ation studies were conducted in vivo and irt vitro using embryonic C57BL/6J mice, A medial preoptic nucleus became discernible using Nissl stain in ma les and females between embryonic days (E) E15 and E17, Cells containing im munoreactive estrogen receptor-alpha were detected in the POA/AH by E13, an d increased in number with age in both sexes, From E15 to E17, examination of the radial glial fiber pattern by immunocytochemistry confirmed the pres ence of dual orientations for migratory guidance ventral to the anterior co mmissure (medial-lateral and dorsal-ventral) and uniform orientation more c audally (medial-lateral), Video microscopy studies followed the migration o f DiI-labeled cells in coronal 250-mu m brain slices from E15 mice maintain ed in serum-free media for 1-3 days. Analyses showed significant migration along a dorsal-ventral orientation in addition to medial-lateral, The video analyses showed significantly more medial-lateral migration in males than females in the caudal POA/AH. In vivo, changes in the distribution of cells labeled by the mitotic indicator bromodeoxyuridine (BrdU) suggested their progressive migration through the POA/AH. BrdU analyses also indicated sign ificant movement from dorsal to ventral regions ventral to the anterior com missure, The significant dorsal-central migration of cells in the POA/AH pr ovides additional support for the notion that the region integrates de deve lopmental information From both telencephalic and diencephalic compartments . The sex difference in the orientation of migration of cells in the caudal POA/AH suggests one locus for the influence of gonadal steroids in the emb ryonic mouse forebrain, (C) 1999 John Wiley & Sons, Inc.