Fig. 1.
Inadequate Tg(Atoh1-cre) upregulation revealed by ROSA26 (a-e, f-j) failed to excise Neurod1 mRNA (a’-e’, f’-j’) in lobule IX and X in Neurod1 mutant cerebellum revealed by in situ hybridization of Neurod1. a-e’ Neurod1f/+, Tg(Atoh1-cre)[control]. f-j’ Neurod1f/f, Tg(Atoh1-cre)[mutant]. a, f In P2 control and mutant cerebella, Tg(Atoh1cre) was prominently expressed from lobule I to VIII, weakly expressed in lobule IX in heterozygous, but completely absent in lobule X. b, g Tg(Atoh1-cre) expression progressed further to lobule IX by P11 and was homogeneously expressed in heterozygous cerebellum but misplaced and condensed in EGL of central lobules in mutant cerebellum. c, h Tg(Atoh1-cre) was expressed uniformly in up to one third of lobule X by P15 in heterozygous cerebellum and dispersed in central lobules in mutant cerebellum. d, i, e, j Tg(Atoh1-cre) expression progressed to half of lobule X in P21 and in adult heterozygous cerebellum (d, e) and was lost in central lobules in mutants (i, j). a’-e’ Neurod1 was expressed uniformly in all the lobules in heterozygous cerebellum as shown by in situ hybridization of Neurod1. f’-j’ Expression of Neurod1 was absent in lobules I to half of VIII in mutant from P2 to adult when Tg(Atoh1-cre) upregulation was prominent. Despite the late upregulation in lobule IX and X, Tg(Atoh1-cre) failed to excise Neurod1 in lobules X, IX, and 1/2VIII in mutant cerebellum. The recombination of Neurod1 by using Tg(Atoh1-cre) must happen in embryonic stages and results in no apparent additional recombination after further upregulation of Tg(Atoh1-cre) as revealed by the expansion of ROSA26-lacZ. h’, i’ Boxed regions are shown at higher magnification in h”, i”, respectively. Bars 250 μm (a-j, a’-j’), 10 μm (h”, i”)