Transcriptome analysis of flathead grey mullet (Mugil cephalus) ovarian development induced by recombinant gonadotropin hormones. Transcriptome of Mugil cephalus ovarian development induced by rFsh and rLh

Single chain recombinant gonadotropin hormones (rGths), recombinant follicle-stimulating hormone (rFsh) and recombinant luteinizing hormone (rLh), produced in Chinese Hamster Ovary cells induced the entire process of vitellogenesis in the flathead grey mullet (Mugil cephalus) and produced viable eggs and larvae. The aim of the present study was to characterize the ovarian molecular pathways and temporal gene expression patterns throughout vitellogenesis induced by rFsh and rLh. For this, five flathead grey mullet females that were arrested at early stages of gonad development were selected from an experimental group and were sampled to follow ovarian development induced with rGths. Briefly, the fish were weekly treated with increasing doses of rFsh —from 6, 9 to 12 µg kg-1 — and after four weeks, rFsh was combined with rLh —increasing doses of 2.5, 4 to 6 µg kg-1—. Then, when oocyte diameter was ≥ 550 µm, only rLh —9 and 12 µg kg-1— was administered on a three-day-basis to complete oocyte growth to ~ 600 µm. Ovarian samples were collected by cannulation from the same five females at four sampling points during the induced gonadal development; (1) before rGth treatment from initial arrested gonad (Stage I), (2) after four weeks of rFsh administration (Stage II), (3) after the combined treatment with rFsh and rLh (Stage III), and (4) after rLh treatment (Stage IV).