West Coast Worm Meeting Abstracts - Caenorhabditis elegans ...

West Coast Worm Meeting 2000
HIM-10 A PROBABLE KINETOCHORE PROTEIN INVOLVED IN
MITOTIC AND MEIOTIC CHROMOSOME SEGREGATION
M. Howe 1 , D G. Albertson 2 , B. J. Meyer 1
1HHMI & Dept. of Mol. Cell Bio. UCB, Berkeley, CA 94720
2CRI, UCSF, San Francisco, CA 94143
The mitotic and meiotic chromosomes of C. elegans are atypical. These mitotic chromosomes are
holocentric, that is, the kinetochore (the structure mediating chromosome attachment to the spindle)
extends along the length of the chromosome. The ultrastructure of these long kinetochores is similar to
those of monocentic chromosomes common to other animals. C. elegans meiotic chromosomes have no
discernable kinetochores at the ultrastructural level. Investigation of C. elegans chromosomes may
identify conserved features of kinetochores essential to chromosome segregation in mitosis and meiosis.
To understand C. elegans kinetochores we have characterized him-10, a gene implicated in mitotic
kinetochore function by an allele that increases free duplication loss. Cloning him-10 revealed that the
gene encodes a novel protein. Protein localization and loss-of-function phenotypes are consistent with
HIM-10 playing a direct role in kinetochore function in mitosis and meiosis.
HIM-10 appears to associate with the kinetochore face of mitotic chromosomes from prophase through
anaphase. HIM-10 staining partially overlaps with a conserved centromeric histone variant HPC-3, with
HIM-10 localizing to the kinetochore region, distal to HPC-3.
him-10 RNAi treatment caused the progeny from injected animals to die as embryos. Fluorescent in situ
hybridization (FISH) to these dead embryos revealed severe aneuploidy suggesting that lethality is due to
aberrant embryonic mitosis. Tubulin staining of dsRNAi embryos showed displaced metaphase
chromosomes, unipolar chromosome attachments, and irregular nuclei. FISH and tubulin staining suggest
that loss of him-10 function causes segregation defects consistent with kinetochore failure.
him-10 is also required during meiosis. The hypomorphic mutation, him-10 (e1511ts), causes a sterility
that can be rescued by mating with wild-type males, suggesting a role for the protein in sperm meiosis.
FISH to dead embryos from the ts sterile adults revealed monosomic and trisomic embryos, suggesting
that the mutation causes chromosome loss in meiosis, not embryonic mitosis. HIM-10 encases
spermatocyte and oocyte chromosomes and duplications, suggesting that a kinetochore-like structure
functions in C. elegans meiosis.
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