The Heterotrimeric G Protein Genes of Caenorhabditis e/egans
21
The GFP fusion constructs of gpa-l, gpa-7, gpa-13, and gpa-1S
showed male-specific expression (Table 1), in addition to the expression
seen in hermaphrodites; the others showed identical staining patterns in
males and hermaphrodites. The expression patterns suggest that C.
elegans uses at least 14 new Ga genes in chemosensory neurons.
2.2.3 The New Ga Genes Are Not Essential
To further analyze the function of all Ga genes in C. elegans we isolated
loss-of-function alleles (Fig. 4), using target selected gene inactivation
(Zwaal et al. 1993; Jansen et al. 1997). Gain-of-function alleles were
generated by introducing the wild-type gene at elevated gene copy
number (XS) as transgenes. All mutants generated in this study and the
previously isolated mutants gpa-2, gpa-2QL, gpa-3, gpa-3QL (Zwaal et
al. 1997), and odr-3 (Roayaie et al. 1998) were tested for phenotypes
(Table 2). The QL mutants overexpress a constitutively active mutant
gene that codes for a protein with strongly reduced GTPase activity.
None of the mutations tested in this study resulted in a lethal phenotype.
Based on the expression patterns, all mutants were tested for subtle
phenotypes.
The gpa-7::GFP expression suggests a function of gpa-7 in regulating muscle or neuron activity, as described for goa-I, gsa-I, and egl-30
(Mendel et aI., 1995; Segalat et al. 1995; Brundage et al. 1996; Korswagen et al. 1997). gpa-7 animals were egg-laying defective and gpa7XS animals were hyperactive regarding egg laying, as measured by the
number of eggs in utero (wild type 12.0±O.6; gpa-7 23.4±1.2; gpa-7XS
6.7±O.6; number of eggs in utero±SEM, in each case n=25). No significant difference could be observed in body wall muscle activity. These
results indicate that gpa-7 possesses a stimulatory function in muscle
cells and/or neurons. Similar functions have been ascribed to gsa-l
(Korswagen et al. 1997) and egl-30 (Brundage et al. 1996). It is interesting to see that although GPA-7 is most similar to Goa, mutations in
gpa-7 result in phenotypes opposite to goa-I, which inhibits the activity
of muscles and neurons (Mendel et al. 1995; Segalat et al. 1995). Taken
together, these data indicate that at least four Ga subunits regulate
muscle and neuron activity in C. elegans: three of the four mammalian
homologues and gpa-7.
21
The GFP fusion constructs of gpa-l, gpa-7, gpa-13, and gpa-1S
showed male-specific expression (Table 1), in addition to the expression
seen in hermaphrodites; the others showed identical staining patterns in
males and hermaphrodites. The expression patterns suggest that C.
elegans uses at least 14 new Ga genes in chemosensory neurons.
2.2.3 The New Ga Genes Are Not Essential
To further analyze the function of all Ga genes in C. elegans we isolated
loss-of-function alleles (Fig. 4), using target selected gene inactivation
(Zwaal et al. 1993; Jansen et al. 1997). Gain-of-function alleles were
generated by introducing the wild-type gene at elevated gene copy
number (XS) as transgenes. All mutants generated in this study and the
previously isolated mutants gpa-2, gpa-2QL, gpa-3, gpa-3QL (Zwaal et
al. 1997), and odr-3 (Roayaie et al. 1998) were tested for phenotypes
(Table 2). The QL mutants overexpress a constitutively active mutant
gene that codes for a protein with strongly reduced GTPase activity.
None of the mutations tested in this study resulted in a lethal phenotype.
Based on the expression patterns, all mutants were tested for subtle
phenotypes.
The gpa-7::GFP expression suggests a function of gpa-7 in regulating muscle or neuron activity, as described for goa-I, gsa-I, and egl-30
(Mendel et aI., 1995; Segalat et al. 1995; Brundage et al. 1996; Korswagen et al. 1997). gpa-7 animals were egg-laying defective and gpa7XS animals were hyperactive regarding egg laying, as measured by the
number of eggs in utero (wild type 12.0±O.6; gpa-7 23.4±1.2; gpa-7XS
6.7±O.6; number of eggs in utero±SEM, in each case n=25). No significant difference could be observed in body wall muscle activity. These
results indicate that gpa-7 possesses a stimulatory function in muscle
cells and/or neurons. Similar functions have been ascribed to gsa-l
(Korswagen et al. 1997) and egl-30 (Brundage et al. 1996). It is interesting to see that although GPA-7 is most similar to Goa, mutations in
gpa-7 result in phenotypes opposite to goa-I, which inhibits the activity
of muscles and neurons (Mendel et al. 1995; Segalat et al. 1995). Taken
together, these data indicate that at least four Ga subunits regulate
muscle and neuron activity in C. elegans: three of the four mammalian
homologues and gpa-7.