title: Molecular development of chondrichthyan claspers and the evolution of copulatory organs.
abstract: The earliest known vertebrate copulatory organs are claspers, paired penis-like structures that are associated with evolution of internal fertilization and viviparity in Devonian placoderms. Today, only male chondrichthyans possess claspers, which extend from posterior pelvic fins and function as intromittent organs. Here we report that clasper development from pelvic fins of male skates is controlled by hormonal regulation of the Sonic hedgehog (Shh) pathway. We show that Shh signalling is necessary for male clasper development and is sufficient to induce clasper cartilages in females. Androgen receptor (AR) controls the male-specific pattern of Shh in pelvic fins by regulation of Hand2. We identify an androgen response element (ARE) in the Hand2 locus and present biochemical evidence that AR can directly bind the Hand2 ARE. Together, our results suggest that the genetic circuit for appendage development evolved an androgen regulatory input, which prolonged signalling activity and drove clasper skeletogenesis in male fins.
authors: Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA.
authors: Katherine L
authors: KL
authors: O'Shaughnessy
authors: Randall D
authors: RD
authors: Dahn
authors: 1] Department of Molecular Genetics and Microbiology, UF Genetics Institute, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA [2] Howard Hughes Medical Institute and Department of Biology, University of Florida, PO Box 103610, Gainesville, Florida 32610, USA.
authors: Martin J
authors: MJ
authors: Cohn
mesh_terms: D000728:Androgens / Q000378:metabolism; D058500:Animal Fins / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D005075:Biological Evolution; D003307:Copulation / Q000502:physiology; D005260:Female; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005835:Genitalia / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D011485:Protein Binding; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D012727:Sex Characteristics; D015398:Signal Transduction; D012860:Skates, Fish / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development
chemical_list: D000728:Androgens; D051792:Basic Helix-Loop-Helix Proteins; D029941:Fish Proteins; D053823:Hedgehog Proteins; D011944:Receptors, Androgen