title: Changes in the expression of alpha-fodrin during embryonic development of Xenopus laevis.
abstract: Fodrin (nonerythroid spectrin) and its associated proteins have been previously implicated in the establishment of specialized membrane-cytoskeletal domains in differentiating cells. Using antiserum which is monospecific for the alpha-subunit of fodrin, we demonstrate that alpha-fodrin is present in oocytes and adult tissues of Xenopus laevis. Analyses of the de novo synthesis of alpha-fodrin during embryonic development reveal that alpha-fodrin is synthesized in oocytes, but not during early development. To investigate the level of control of alpha-fodrin expression, we isolated two cDNA clones for oocyte alpha-fodrin. The oocyte cDNA clones were identified as encoding portions of alpha-fodrin based on DNA sequence analysis and on the comparison of the predicted amino acid sequence of the cDNAs with the known sequence of human erythrocyte alpha-spectrin. The Xenopus alpha-fodrin cDNAs hybridize to a transcript of approximately 9 kb on RNA blots, and probably to a single gene type on genomic DNA blots. Both RNA blot analyses and S1 nuclease protection assays with the Xenopus alpha-fodrin cDNAs demonstrate that the observed decline in the de novo synthesis of alpha-fodrin polypeptides is controlled by a dramatic decrease in the abundance of alpha-fodrin transcripts after fertilization. In contrast, levels of actin transcripts do not decrease during this period. Inasmuch as steady-state levels of alpha-fodrin transcripts rise by the neurula stage of development, these results suggest that the synthesis of alpha-fodrin polypeptides during embryonic development of Xenopus is regulated, rather than constitutive, and that the primary level of control is the steady-state abundance of mRNA.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D004262:DNA Restriction Enzymes; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005260:Female; D008565:Membrane Proteins / Q000235:genetics*; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics*; D009865:Oocytes / Q000378:metabolism*; D014158:Transcription, Genetic; D014982:Xenopus laevis; D013049:Spectrin
chemical_list: D002352:Carrier Proteins; D004247:DNA; D004262:DNA Restriction Enzymes; D008565:Membrane Proteins; D008840:Microfilament Proteins; D013049:Spectrin