Worm Breeder's Gazette 9(2): 26
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We are continuing to study the genomic organization of expressed MSP genes and MSP pseudogenes by physical mapping of cloned genes (WBG Vol. 8,3 p. 61). We have now examined a total of 39 different MSP genes. Thirty of these genes are grouped into 5 clusters of 3 to 6 genes each. The other 9 genes are isolated on small contigs. The MSP genes of a given cluster are grouped within about 50 Kb of DNA but are not in tandem arrays; they are separated by 2-10 Kb of DNA. The clusters are surrounded by DNA free of MSP genes . Genes with similar 3' untranslated sequences are found in the same cluster. Four of the five clusters have been mapped to chromosomes by overlap with known genes or in situ hybridization. One cluster of six genes is adjacent to col-2 on chromosome IV. Another cluster of 5 genes maps on the left side of IV. Two other clusters map to the same location on the left side of chromosome II perhaps near dpy-10. In addition to the MSP genes in the gene cluster near col-2, three genomic lambda clones which may contain other sperm-specific genes map within this cluster. This suggests that this may be a general cluster of sperm-specific genes, perhaps reflecting common functional or regulatory interactions. It is unlikely that the multiple clusters of MSP genes arose by duplication of an initial cluster. It is more likely that genes have duplicated themselves nearby. The similarity in sequence of nearby genes could represent evolutionarily recent duplication or gene conversion of nearby genes. Further sequence analysis may distinguish these possibilities. Of the sequenced or carefully probed genes, about half are incomplete pseudogenes missing their 5' or 3' ends or containing insertions in the coding sequences. These are intermingled among the expressed genes in the two clusters analyzed. The coding sequences remaining in these pseudogenes are still highly homologous to complete MSP genes suggesting that the defects in these genes are of recent origin. We are presently mapping the contigs containing MSP gene clusters on chromosome II and the contig containing col-2 on chromosome IV by trying to find overlaps between cosmids and known deletion breakpoints. If anyone else has identified clones which overlap deletion breakpoints in these regions please let us know.