IDENTIFICATION, MOLECULAR CHARACTERISATION OF CATENIN ß HOMOLOG FROM REDLIP MULLET Liza haematocheila
Catenin β was first identified as a Ca2+ dependent cell adhesion molecule in the cytoskeletal structure together with catenin α and ɤ. The function of catenin β was elaborated to the central signaling transducer in the Wnt signaling pathway. The cytoplasmic catenin β concentration is highly controlled by β-catenin disruption complex. Unless Wnt ligand enables the signaling cascade, the catenin β remain in the cytoplasm at low concentrations. However, catenin β can regulate nearly 400 genes which involve cell survival, apoptosis, growth, differentiation, and immune functions after the translocation to the nucleus. The current study was designed to investigate the transcriptional variation of catenin β of red lip mullet after the bacterial and viral pathogenic mimicry.
Catenin β sequence was identified from the constructed cDNA library of redlip mullet. Bioinformatics software and online tools were employed to characterize the identified nucleotide sequence and predicted the amino acid sequence. Healthy red lip mullets were dissected and 12 tissues including peripheral blood leucocytes, head kidney, kidney, liver, gill, and spleen were harvested to isolate mRNA and synthesize cDNA. The cDNA was used to evaluate the transcriptional difference of catenin β in different tissues in healthy redlip mullets. Healthy fish were challenged with IP injections of LPS, Poly I:C and live Lactococcus garvieae. The spleen was dissected at 0, 6, 24, 48 and 72 hour time points after the challenge. mRNA isolation and cDNA synthesis were performed and the qPCR was used to investigate the fold change of catenin β mRNA transcription.
The redlip mullet catenin β gene is composed of 2352 bp and predicted amino acid sequence composed with 783AA. The phylogenetic analysis cladded the sequence with other known fish catenin β homologs. However, the multiple sequence alignment shows the active domain structure of redlip mullet bears a resemblance to human catenin β. Therefore a similar function of human catenin β may observe in mullet. However, unlikely to humans the highest expression of catenin β mRNA was observed in heart muscles of mullet. The catenin β expression is drastically downregulated by different PAMP's. Previous reports documented that catenin β can affect the localization of NF-κB transcription factors preventing further induction of downstream genes. Therefore, the activity of NF-κB might be enhanced by downregulating catenin β. However, more experiments are required to reveal the functions of fish catenin β.
