A zinc knuckle gene on the Y chromosome (zkY) determines sex in Atlantic cod (Gadus morhua)

Studying the variety of sex determining genes in teleost fish may contribute to increase our understanding of sex chromosome evolution in vertebrates. To date, no sex determinant is known for the superorder Paracanthopterygii, comprising about 1340 species, including the commercially important Atlantic cod. In this study we characterize a Y-specific region of 9 kb (on linkage group 11) containing a single gene named zkY for zinc knuckle on the Y chromosome. The gene is transcribed at high levels in larvae before commencement of sex differentiation and encodes a novel zinc knuckle protein that putatively binds RNA target sequences. We propose that cod zkY suppresses germ cell proliferation in the developing males by interacting with the germ-cell specific RNA regulatory network. For 1 and 7 dph larvae, RNA was extracted from a pool of 10 individuals using the Qiagen AllPrep DNA/RNA/miRNA Universal kit (Qiagen; Germany). Samples were prepared for sequencing using TruSeq Stranded mRNA kit from Illumina (USA) and sequenced using an Illumina HiSeq 2000 to produce 362 million reads. For the samples 12 and 35 dph samples, RNA was extracted using an RNeasy kit (Qiagen, Germany) prepared for sequencing using TruSeq Stranded mRNA kit from Illumina (USA) and sequenced using an Illumina MiSeq (2 x 250nt) to produce 4.4 million reads.