Gene expression during ovarian differentiation in parasitic and non-parasitic lampreys: Implications for fecundity and life history types
Summary
Lampreys diverged from the jawed vertebrate lineage approximately 500 million years ago. Lampreys 28 undergo sex differentiation much later than most other vertebrates, and ovarian differentiation occurs 29 several years before testicular differentiation. The genetic basis of lamprey sex differentiation is of par- 30 ticular interest both because of the phylogenetic importance of lampreys and because of their unusual 31 pattern of sex differentiation. As well, differences between parasitic and non-parasitic lampreys may first 32 become evident at ovarian differentiation. However, nothing is known about the genetic basis of ovarian 33 differentiation in lampreys. This study examined potential differences in gene expression before, during, [...]
Summary
Lampreys diverged from the jawed vertebrate lineage approximately 500 million years ago. Lampreys 28
undergo sex differentiation much later than most other vertebrates, and ovarian differentiation occurs 29
several years before testicular differentiation. The genetic basis of lamprey sex differentiation is of par- 30
ticular interest both because of the phylogenetic importance of lampreys and because of their unusual 31
pattern of sex differentiation. As well, differences between parasitic and non-parasitic lampreys may first 32
become evident at ovarian differentiation. However, nothing is known about the genetic basis of ovarian 33
differentiation in lampreys. This study examined potential differences in gene expression before, during, 34
and after ovarian differentiation in parasitic chestnut lamprey Ichthyomyzon castaneus and non-parasitic 35
northern brook lamprey Ichthyomyzon fossor. Eight target genes (17b-hydroxysteroid dehydrogenase, 36
germ cell-less, estrogen receptor b, insulin-like growth factor 1 receptor, daz-associated protein 1, cyto- 37
chrome c oxidase subunit III, Wilms’ tumour suppressor protein 1, and dehydrocholesterol reductase 7) 38
were examined. Northern brook lamprey displayed higher expression of cytochrome c oxidase subunit III, 39
whereas chestnut lamprey displayed higher expression of insulin-like growth factor 1 receptor; these 40
genes may be involved in apoptosis and oocyte growth, respectively. Presumptive male larvae had higher 41
expression of Wilms’ tumour suppressor protein 1, which may be involved in the undifferentiated gonad 42
and/or later testicular development. Differentiated females had higher expression of 17b hydroxysteroid 43
dehydrogenase and daz-associated protein 1, which may be involved in female development. This study 44
is the first to identify genes that may be involved in ovarian differentiation and fecundity in lampreys.
