Cloning and expression pattern of Siglec-4b like in Oreochromis niloticus

We cloned the sialic acid-binding immunoglobulin superfamily lectin Siglec-4b like gene from neutrophilic granulocyte of Oreochromis niloticus, and then analyzed its sequence by bioinformatics approach and detected its mRNA expression levels during embryonic development and in tissues before and after artificial infection of Streptococcus agalactiae (GBS) by qPCR. The analysis shows that Siglec-4b like had specific domains and conservative amino acid residues similar to mammalian Siglec-4. During the embryonic development, a certain amount of Siglec-4b like expressed in eggs, and the expression increased after fertilization. As embryo developed, the expression continued to rise and reached the maximum amount at 7 hpf and then decreased gradually. Siglec-4b like mRNA was ubiquitously expressed in all the tested tissues of tilapia, and the expression levels were relatively high in gill, muscle, skin, head kidneys and intestines but very low in the other tested tissues. After being infected with GBS, the expression of Siglec-4b like in gill, head kidneys, intestines, muscle and skin decreased. The results provide references for further research on immune escape mechanism of GBS and regulation effect of Siglec-4b like on tilapia immune system.