CHARACTERIZATION OF A CDNA-ENCODING A NOVEL BAND 4.1-LIKE PROTEIN IN ZEBRAFISH

Membrane skeleton protein 4.1 and other members of a family of protein s that link the cytoskeleton to the plasma membrane may play an integr al role in cell communication during development. The polymerase chain reaction and degenerate oligodeoxynucleotide primers to consensus seq uences in the putative membrane-binding domain of the protein 4.1 supe rfamily were used to isolate cDNAs encoding members of the zebrafish p rotein 4.1 family. Zebrafish stage-and tissue-specific first strand cD NA was used in the PCR. After the reaction, amplicons of the predicted size were sequenced to confirm their relationship to the protein 4.1 superfamily. One cDNA, with a high degree of similarity to a mouse nov el band 4.1-like cDNA, was used to probe a zebrafish adult brain libra ry. A 2.4-kb cDNA was isolated and found to encode a 619 amino acid po lypeptide homologous to mouse novel band 4.1-like protein 4. Zebrafish nbl4 mRNA is maternally supplied and is expressed throughout embryoge nesis. In adults, nbl4 is found in the ovary, eye, heart, and brain, b ut not in gut or skeletal muscle. When synthetic nbl4 mRNA is translat ed in vitro it binds calmodulin in a calcium-dependent manner. These d ata indicate that zebrafish nbl4 is a maternal transcript owing to its presence before the midblastula transition, and it is present later o n in specific adult structures. The ability to bind calmodulin would s uggest that the function of nbl4 protein may be potentially regulated via a calcium-calmodulin dependent mechanism.