Figure 3.
mab-9 Is a Class-Specific Regulator of Motor Neuron Identity(A) Expression of
unc-129 is lost in
mab-9(
ot720) animals (phenocopied by
gk396730 and
e2410). In the double mutant, the phenotype of
bnc-1 is epistatic to thatof
mab-9, indicating that MAB-9 represses
bnc-1.
mab-9 cDNA driven by the
unc-3 promoter in
mab-9 mutants rescues the
unc-129 expression loss phenotypein DA/DB and is sufficient to ectopically derepress
unc-129 in VA/VB MNs. Similarly,
unc-53 expression in DA MNs is lost (albeit only in the anterior half of the VNC)in
mab-9(
ot788). WT images repeated from Figures 2A and 2G; red pharyngeal expression marks the
unc-3prom::
mab-9 transgene. All scale bars represent 50 um.(B) Quantification for (A); error bars show the SD. Unpaired t tests were performed for all mutants compared to WT. ***p < 0.001 (n R 13).(C)
mab-9 gene locus. The endogenous reporter is not visible in the VNC.(D)
bnc-1 is derepressed in DA/DB MNs in
mab-9 mutants. WT image repeated from Figure 2E. A
bnc-1 promoter 1.8 kb upstream of the start codon recapitulatesthe VA/VB-specific expression of endogenous
bnc-1. Mutation (mut-) of MAB-9 binding sites causes
bnc-1 to be derepressed in DA/DB MNs. All rfp representsmchopti+
h2b. See Figure S1H for quantification.(E)
bnc-1 fluorescent reporters of the endogenous gene locus (CRISPR; see Figure 2E), a fosmid (see Figure S1G), the rescue construct used in Figures 2A and 2B(see Figure S1G), and the abovementioned 1.8-kb promoter (see Figure 3D) express specifically in VA/VB MNs. Deletion of MAB-9 binding sites (white-filledvertical rectangle) causes
bnc-1 to be derepressed in DA/DB MNs. See Figure S1H for quantification.(F)
del-1 is expressed in VA/VB MNs and is regulated by
unc-3. In
mab-9 mutants,
del-1 is derepressed in DA/DB MNs in an
unc-3-dependent manner. Theunc-3prom::
mab-9 transgene rescues this phenotype and is sufficient to ectopically repress
del-1 in VA/VB MNs. Similarly,
unc-3-dependent
inx-12, which isVA/VB specific, is also derepressed in DA/DB MNs in
mab-9 mutants.(G) Quantification for (F) and the derepression of
unc-3-dependent, VA/VB-specific
lgc-36 in DA/DB MNs in
mab-9 mutants (see Figure S1I for images); error barsshow the SD. Unpaired t tests were performed for all mutants compared to WT. ***p < 0.001 (n R 13).(H) Genetic model depicting MAB-9 repressing BNC-1 as well as VA/VB-specific effector genes in DA/DB MNs.