Ca²⁺ influx-linked protein kinase C activity regulates the β-catenin localization, micromere induction signalling and the oral-aboral axis formation in early sea urchin embryos.
Sea urchin embryos initiate cell specifications at the 16-cell stage by forming the mesomeres, macromeres and micromeres according to the relative position of the cells in the animal-vegetal axis. The most vegetal cells, micromeres, autonomously differentiate into skeletons and induce the neighbouring macromere cells to become mesoendoderm in the β-catenin-dependent Wnt8 signalling pathway. Although the underlying molecular mechanism for this progression is largely unknown, we have previously reported that the initial events might be triggered by the Ca2+ influxes through the egg-originated L-type Ca2+ channels distributed asymmetrically along the animal-vegetal axis and through the stretch-dependent Ca2+channels expressed specifically in the micromere at the 4th cleavage. In this communication, we have examined whether one of the earliest Ca2+ targets, protein kinase C (PKC), plays a role in cell specification upstream of β-catenin. To this end, we surveyed the expression pattern of β-catenin in early embryos in the presence or absence of the specific peptide inhibitor of Hemicentrotus pulcherrimus PKC (HpPKC-I). Unlike previous knowledge, we have found that the initial nuclear entrance of β-catenin does not take place in the micromeres, but in the macromeres at the 16-cell stage. Using the HpPKC-I, we have demonstrated further that PKC not only determines cell-specific nucleation of β-catenin, but also regulates a variety of cell specification events in the early sea urchin embryos by modulating the cell adhesion structures, actin dynamics, intracellular Ca2+ signalling, and the expression of key transcription factors.
Department of Biological Sciences,Tokyo Metropolitan University,Minamiohsawa 1-1,Hachiohji-shi,Tokyo 192-0397,Japan.
Ikuko
I
Yazaki
Misaki Marine Biological Station,University of Tokyo,Miura,Japan.
Toko
T
Tsurugaya
Stazione Zoologica Anton Dohrn,Villa Comunale 1-80121 Napoli,Italy.
Luigia
L
Santella
Stazione Zoologica Anton Dohrn,Villa Comunale 1-80121 Napoli,Italy.
Jong Tai
JT
Chun
Stazione Zoologica Anton Dohrn,Villa Comunale 1-80121 Napoli,Italy.
Gabriele
G
Amore
LSL Co. Ltd,Nerima-ku Tokyo 178-0061,Japan.
Shinichiro
S
Kusunoki
Department of Biological Sciences,Tokyo Metropolitan University,Minamiohsawa 1-1,Hachiohji-shi,Tokyo 192-0397,Japan.
Akiko
A
Asada
Department of Anatomy,St. Marianna University School of Medicine,Sugao,Kawasaki,Kanagawa 216-8511,Japan.
Tatsuru
T
Togo
Misaki Marine Biological Station,University of Tokyo,Miura,Japan.
Koji
K
Akasaka
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004475:Ectoderm / Q000187:drug effects / Q000196:embryology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005775:Gastrula / Q000187:drug effects / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008297:Male; D008969:Molecular Sequence Data; D009055:Mouth / Q000166:cytology / Q000196:embryology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012617:Sea Urchins / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction; D051176:beta Catenin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000199:Actins; D047428:Protein Kinase Inhibitors; D051176:beta Catenin; D011493:Protein Kinase C; D002118:Calcium
Sea urchin embryo