Identification and Embryonic Expression of a Highly Conserved Meis-Linked Gene

Using a comparative genomics approach we have identified a novel and previously undescribed gene in zebrafish, zgc:154061, which we have temporarily named meis2 linked gene (m2lg). This gene is located directly downstream of the zebrafish meis2.2 gene. M2lg and its vertebrate orthologs are organized in a convergently transcribed manner with respect to the Meis2 gene in all species we have examined (meis2.2 in zebrafish). During zebrafish development, transcripts of m2lg are observed in every cell of the embryo from the earliest stage through the shield stage indicating this gene is a maternal transcript since its expression precedes the activation of the zygotic genome at the midblastula transition. Expression of m2lg gradually decreases from its peak value at 0 hours past fertilization (hpf) until 8 hpf and then is observed to be activated again at 12 hpf as determined by quantitative real time polymerase chain reaction (PCR). Western blots show that the protein is translated and expressed as early as 2 hpf and is present in significant amounts until 12 hpf. Immunohistochemistry on 48 hpf zebrafish embryo cross-sections show that the protein is present and is highly localized to the retinal area and the optic nerve.