title: Focal adhesion kinase and paxillin: novel regulators of brain sexual differentiation?
abstract: Steroid-mediated sexual differentiation of the brain is a developmental process that permanently organizes the brain into a male or female phenotype. Previous studies in the rodent have examined the steroid-mediated mechanisms of male brain development. In an effort to identify molecules involved in female brain development, a high-throughput proteomics approach called PowerBlot was used to identify signaling proteins differentially regulated in the neonatal male and female rat hypothalamus during the critical period for brain sexual differentiation. Focal adhesion kinase (FAK) and paxillin, both members of the focal adhesion complex family of proteins, were significantly elevated in the newborn female compared with the male hypothalamus. Sex differences in these proteins were not detected in brain regions that are not subject to substantial organizational effects of steroids. Estrogens, the aromatized products of testosterone in the male, can both masculinize and defeminize the male brain. Daily estradiol administration to neonatal females significantly reduced FAK and paxillin in the hypothalamus, and aromatase inhibition increased paxillin in males to levels comparable with females. Androgens also appear to modulate paxillin levels in combination with estrogen action. Across development, hypothalamic levels of FAK were significantly elevated in females compared with males on postnatal d 6. Synaptic circuits in the hypothalamus develop sex differences perinatally. Estradiol treatment of cultured hypothalamic neurons significantly enhanced axon branching (P<0.01), consistent with the phenotype of FAK-deficient neurons. Together, these data implicate FAK and paxillin as regulators of sex differences in neuronal morphology.
authors.affiliation: Department of Physiology and Program in Neuroscience, University of Maryland, Baltimore, Baltimore, Maryland 21201, USA. debspeert@gmail.com
authors.forename: Debra B
authors.initials: DB
authors.lastname: Speert
authors.forename: Anne T M
authors.initials: AT
authors.lastname: Konkle
authors.forename: Susan L
authors.initials: SL
authors.lastname: Zup
authors.forename: Jaclyn M
authors.initials: JM
authors.lastname: Schwarz
authors.forename: Chaitanya
authors.initials: C
authors.lastname: Shiroor
authors.forename: Michael E
authors.initials: ME
authors.lastname: Taylor
authors.forename: Margaret M
authors.initials: MM
authors.lastname: McCarthy
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001141:Aromatase / Q000187:drug effects; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D007150:Immunohistochemistry; D000077289:Letrozole; D008297:Male; D016501:Neurites / Q000187:drug effects; D009570:Nitriles / Q000494:pharmacology; D051419:Paxillin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000037:antagonists & inhibitors; D012733:Sex Differentiation; D012737:Sex Factors; D013629:Tamoxifen / Q000494:pharmacology; D013739:Testosterone / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology
chemical_list: D009570:Nitriles; D051419:Paxillin; D011960:Receptors, Estrogen; D014230:Triazoles; D013629:Tamoxifen; D013739:Testosterone; D004958:Estradiol; D000077289:Letrozole; D001141:Aromatase; D051416:Focal Adhesion Protein-Tyrosine Kinases