| Budget Amount *help |
¥3,860,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,300,000 (Direct Cost: ¥2,300,000)
|
|---|
| Research Abstract |
A major shell matrix protein originally obtained from a freshwater snail is a molluscan homologue of Dermatopontins, a group of Metazoan proteins also called TRAMP (Tyrosine-rich acidic matrix protein). We sequenced and identified 14 molluscan homologues of Dermatopontin from 2 basommatophoran and 6 stylommatophoran snail species. The bassommatophoran Dermatopontins fell into three types, one is suggested to be a shell matrix protein and the others are proteins having more general functions based on gene expression analyses. N-glycosylation is inferred to be important for the function involved in shell calcification from comparison of primary structures of basommatophoran Dermatopontins、 The stylommatophoran Dermatopontins fall into two types, also suggested to comprise a shell matrix protein and a protein having a more general function. Phylogenetic analyses using Neighbor-joining, Maximum likelihood and Bayesian methods revealed gene duplication events occurred independently in both
… More
basommatophoran and stylommatophoran lineages. These results suggest that the dermatopontin gene were co-opted for molluscan calcification at least twice independently after the divergence of basommatophoran and stylommatophoran lineages, or in more recent years than we have expected.
In order to know the role of Dermatopontin, we used RNA interference (RNAi). At first, we examined whether RNAi worked in L stagnalis, with RT-PCR. The results of RT-PCR indicated that RNAi works effectively in L stagnalis. But we could not observe any significant effects of RNAi for dermatopontin on shell formation. We examined the presence of Dermatopontin in the extrapallial fluid of the individuals injected with dsRNA for dermatopontin using immunological assays. Antiserum raised against Dermatopontin fragment showed significant immunological reactivity with the extrapallial fluid suggesting that the presence of Dermatopontin.
Biominerals, especially molluscan shells, generally contain unusually acidic proteins. These proteins are believed to function in crystal nucleation and inhibition. We previously identified an unusually acidic protein Aspein from the pearl oyster Pinctada fucata. Here we show that Aspein can control the CaCO3 polymorph (calcite/aragonite) in vitro. While aragonite is preferentially formed in Mg2+-rich solutions imitating the extrapallial fluids of marine molluscs, Aspein exclusively induced calcite precipitation. Our results suggest that Aspein is involved in the specific calcite formation in the prismatic layer. Experiments using truncated Aspein demonstrated that the aspartic acid rich domain is crucial for the calcite precipitation.
Soluble proteins in Haliotis gigantean shells were characterized using biochemical and molecular biological techniques. SDS-PAGE revealed two major protein bands, 42 kDa and 41 kDa when stained with Coomassie Brilliant Blue (CBB). Periodic acid Schiff staining and stains-all staining indicated that these proteins are glycosylated and cation-binding potential. The cDNA for these proteins isolated by PCR, revealing that these two proteins rae homolog of Nacrein. Phylogenetic analyses using Neighbor-joining, method revealed that NG-rich repeats in Nacrein occurred independently in both gastropod and bivalve lineages. Less
|
