title: Meiotic wave adds extra asymmetry to the development of female chicken gonads.
abstract: Development of female gonads in the chicken is asymmetric. This asymmetry affects gene expression, morphology, and germ cell development; consequently only the left ovary develops into a functional organ, whereas the right ovary remains vestigial. In males, on the other hand, both gonads develop into functional testes. Here, we revisited the development of asymmetric traits in female (and male) chicken gonads between Hamburger Hamilton stage 16 (HH16) and hatching. At HH16, primordial germ cells migrated preferentially to the left gonad, accumulating in the left coelomic hinge between the gut mesentery and developing gonad in both males and females. Using the meiotic markers SYCP3 and phosphorylated H2AFX, we identified a previously undescribed, pronounced asymmetryc meiotic progression in the germ cells located in the central, lateral, and extreme cortical regions of the left female gonad from HH38 until hatching. Moreover, we observed that--in contrast to the current view--medullary germ cells are not apoptotic, but remain arrested in pre-leptotene until hatching. In addition to the systematic analysis of the asymmetric distribution of germ cells in female chicken gonads, we propose an updated model suggesting that the localization of germ cells--in the left or right gonad; in the cortex or medulla of the left gonad; and in the central part or the extremities of the left cortex--has direct consequences for their development and participation in adult reproduction.
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: Ana
authors.initials: A
authors.lastname: de Melo Bernardo
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: A Marijne
authors.initials: AM
authors.lastname: Heeren
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: Liesbeth
authors.initials: L
authors.lastname: van Iperen
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: Maria Gomes
authors.initials: MG
authors.lastname: Fernandes
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: Nannan
authors.initials: N
authors.lastname: He
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: Stafford
authors.initials: S
authors.lastname: Anjie
authors.affiliation: Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Noce
authors.affiliation: Department of Genetics, Ribeirao Preto Medical School, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Ester Silveira
authors.initials: ES
authors.lastname: Ramos
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Centre, Leiden, the Netherlands.|Department for Reproductive Medicine, Ghent University Hospital, Ghent, Belgium.
authors.forename: Susana M Chuva
authors.initials: SM
authors.lastname: de Sousa Lopes
mesh_terms: D000818:Animals; D019521:Body Patterning; D002465:Cell Movement; D002645:Chickens; D047108:Embryonic Development; D000066473:Embryonic Germ Cells / Q000166:cytology*; D005260:Female; D008297:Male; D008540:Meiosis; D049469:Meiotic Prophase I; D010053:Ovary / Q000196:embryology*; D012727:Sex Characteristics; D013737:Testis / Q000196:embryology