Title

Isolation of long-lived mutants in the nematode Caenorhabditis elegans and characterization of the new mutants

Date of Award

1998

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biology

First Committee Member

David L. Wilson, Committee Chair

Abstract

The biological causes of aging are still largely uncertain. However, clearly genetic factors play an important role in organismic aging. The nematode Caenorhabditis elegans has been used as a model organism to investigate the genetic basis of aging.I have isolated four new aging mutants exhibiting increased life expectancy in C. elegans. These mutants were isolated from progeny of EMS-treated wild-type hermaphrodites (strain N2). One of the mutants was isolated through an established method. This mutant, named yw23 (strain HG23), exhibits about 20% longer lifespan than the wild-type strain, N2. The other three mutants, HG25, HG96, HG246, were isolated by using a novel procedure that involves using heat shock as a means to screen a large number of animals and isolate a few animals that appear to be more resistant to heat shock. The characteristics of these four mutants were examined.The mutant yw23 was studied in more detail. I have outcrossed HG23 once. From the self-progeny of the F1 hybrids of HG23 and N2, one strain that lived longer than N2 has been isolated and named HG231(yw23). HG231 also lives about 20% longer than N2.HG23 and HG231 hermaphrodites have reduced fertility than that of N2. They have a normal body size and a normal appearance. Their mating behavior, feeding behavior and locomotive behavior all appear normal. In liquid, HG231 shows a slightly higher swimming rate than that of N2. HG231 hermaphrodites develop slower than N2 hermaphrodites.Genetic experiments indicated that the mutation yw23 that extends the mutant's lifespan is recessive to the wild-type allele. yw23 complements all the currently known long-lived mutants, such as age-1, daf-2, and clk-1 mutants, indicating the mutation is in a gene that is different from all the currently known genes that regulate the longevity of C. elegans. So this appears to be a novel longevity gene and we name it as age-2.When age-2 (yw23) was combined with the age-1 mutant (strain TJ401), a double mutant has been isolated from the F4 self progeny of the F1 hybrids. This double mutant was named HG284. HG284 animals show a lifespan that is longer than that of either yw23 or the age-1 (TJ401) alone. HG284 can live more than twice as long as N2. HG284 appears unique in that it lives slightly longer at 25$\sp\circ$C than at 20$\sp\circ$C, contrary to all the other known long-lived mutants in C. elegans.I have mapped the mutation that extends the lifespan of yw23 mutant animals to Chromosome I. The mapping was done by using the method of genetic mapping with polymorphic sequence-tagged sites (single worm PCR based mapping).

Keywords

Biology, Genetics

Link to Full Text

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