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Published January 15, 1984 | public
Journal Article

Sea urchin actin gene subtypes

Abstract

The actin gene family of the sea urchin Strongylocentrotus purpuratus was analyzed by the genome blot method, using subcloned probes specific to the 3′ terminal non-translated actin gene sequence, intervening sequence and coding region probes. We define an actin gene subtype as that gene or set of genes displaying homology with a given 3′ terminal sequence probe, when hybridized at 55°C, 0·75 m-Na+. By determining the often polymorphic restriction fragment band pattern displayed in genome blots by each probe, all, or almost all of the actin genes in this species could be classified. Our evidence shows that the S. purpuratus genome probably contains seven to eight actin genes, and these can be assigned to four subtypes. Studies of the expression of the genes (Shott et al., 1983) show that the actin genes of three of these subtypes code for cytoskeletal actins (Cy), while the fourth gives rise to a muscle-specific actin (M). We denote the array of S. purpuratus actin genes indicated by our data as follows. There is a single CyI actin gene, two or possibly three CyII genes (CyIIa, CyIIb, and possibly CyIIc), three CyIII actin genes (CyIIIa, CyIIIb, CyIIIc), and a single M actin gene. Comparative studies were carried out on the actin gene families of five other sea urchin species. At least the CyIIa and CyIIb genes are also linked in the Strongylocentrotus franciscanus genome, and this species also has a CyI gene, an M actin gene and at least two CyIII actin genes. It is not clear whether it also possesses a CyIIc actin gene, or a CyIIIc actin gene. The genome of a more closely related congener, Strongylocentrotus dröbachiensis, includes 3′ terminal sequences suggesting the presence of a CyIIc gene. In S. franciscanus and S. dröbachiensis the first intron of the CyI gene has remained homologous with intron sequences of both the CyIIa and CyIIb genes, indicating a common origin of these three linked cytoskeletal actin genes. Of the four S. purpuratus 3′ terminal subtype probe sequences only the CyI 3′ terminal sequence has been conserved sufficiently during evolution to permit detection outside of the genus Strongylocentrotus. An unexpected observation was that a sequence found only in the 3′ untranslated region of the CyII actin gene in the DNA of S. dröbachiensis and S. purpuratus is represented as a large family of interspersed repeat sequences in the genome of S. franciscanus.

Additional Information

© 1984 Academic Press Inc. (London) Ltd. Received 26 July 1983, and in revised form 20 September 1983. Edited by W. Franke. The authors are grateful to Professor Elias Lazarides of this Institute for reviewing this manuscript. We are pleased to acknowledge the assistance of Professor Marvin Rosenberg of California State University, Fullerton and Mr R. Wek in some of the sequence determinations and other experiments. We thank Mr Gary Mockli, who was supported by a Summer Undergraduate Research Fellowship, for his assistance. We are also most pleased to acknowledge the skilful and perseverant assistance of: Ms Stephanie Canada in the preparation of the manuscript. This research was supported by National Institutes of Health grant GM 20927. One of us (J.J.L.) was supported by a National Institutes of Health training grant (GM-07616), another (R.J.S.) by a long-term European Molecular Biology Organisation fellowship, and another (S.J.R.) by an American Cancer Society fellowship (PF-2054).

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023