Genetic modifiers of otocephalic phenotypes in Otx2 heterozygous mutant mice
Takuichiro Hide1,2,
Jun Hatakeyama1,
Chiharu Kimura-Yoshida1,3,
E Tian1,
Naoki Takeda4,
Yukitaka Ushio2,
Toshihiko Shiroishi5,
Shinichi Aizawa1,3,*,
and
Isao Matsuo1,3
Present address: Vertebrate Body Plan Group, RIKEN Center for Developmental Biology, 2-2-3 Minatojima Minami Cho, Chuou-Ku, Kobe, Hyougo 650-0047, Japan
1 Department of Morphogenesis, Institute of Molecular Embryology and Genetics (IMEG), Kumamoto University, Honjo 2-2-1, Kumamoto 860-0811, Japan
2 Department of Neurosurgery, Kumamoto University School of Medicine, Kumamoto University, Honjo 2-2-1, Kumamoto 860-0811, Japan
3 Vertebrate Body Plan Group, RIKEN Center for Developmental Biology, 2-2-3 Minatojima Minami Cho, Chuou-Ku, Kobe, Hyougo 650-0047, Japan
4 Division of Transgenic Technology, Center for Animal Resources and Development (CARD), Kumamoto University, Honjo 2-2-1, Kumamoto 860-0811, Japan
5 Department of Mammalian Development, National Institute of Genetics, Mishima, Japan
View larger version (94K):
[in a new window]
|
Fig. 1. Variation of external craniofacial morphology of Otx2 heterozygous mutant embryos at 18.5 dpc. (A) Wild-type mouse backcrossed Otx2 knockout chimeras with wild-type B6 females. Otx2 heterozygous mutant mice (N2) backcrossed Otx2 mutant chimeras with wild type CBA females (B) and with wild type B6 females (C-I). No noticeable malformations are evident in the mutant mouse on the CBA strain genetic background (B). The severity of the phenotype varies from normal to acephaly (C-I). No apparent external abnormalities are observed in the mutant mouse on the B6 strain genetic background (C). The mutant mouse displays reduction of the lower jaw (D). The mutant mouse lacks an entire lower jaw (E). The mutant mouse displays excencephaly (F). The distal region of the face is shortened in the mutant mouse (short nose) (G). The face is cleft in the mutant mouse (cleft face) (H). The entire head is lacking (acephaly) in the mutant mouse (I).
|
|
View larger version (15K):
[in a new window]
|
Fig. 2. Frequency distribution of external malformations in mutant mice with B6 background. (A) Otx2 heterozygous mutant N2 embryos (n=200) at 18.5 dpc obtained by backcrossing chimeras with wild-type B6 females are phenotypically classified into eight groups according to their external morphology. (B) Otx2 heterozygous mutant N3 embryos (n=200) at 18.5 dpc obtained by backcrossing the N2 male with wild-type B6 females are phenotypically classified into eight groups according to their external morphology.
|
|
View larger version (74K):
[in a new window]
|
Fig. 3. Variation of mandible length in Otx2 heterozygous mutant mice. Whole-mount views of skull morphology of wild type (A,B) and heterozygous mutant embryos (C-K) at 18.5 dpc following cartilage and bone staining. Mandibles have been separated in cases in which they were present (A-J). (K) An embryo lacking a mandible. The length of each mandible from proximal to distal is 5.4 mm (A), 5.4 mm (C), 4.2 mm (E), 2.8 mm (G) and 1.4 mm (I). an, angular process; as, alisphenoid; bs, basisphenoid; bo, basioccipital; cd, condyloid process; co, coronoid process; eo, exoccipital; mx, maxillar; pl, palatine; pm, premaxillar; sy, symphysis.
|
|
View larger version (14K):
[in a new window]
|
Fig. 4. Frequency distribution of mandible length in 18.5 dpc embryos. Distribution of mandible length in N2 wild-type embryos (n=30) chimeras crossed with wild type B6 females (A), heterozygous N2 mutants (n=200) crossed with wild-type B6 females (B) and heterozygous N3 mutants (n=200) backcrossed twice with wild-type B6 females (C).
|
|
View larger version (27K):
[in a new window]
|
Fig. 5. Chromosomal location of microsatellite markers selected for analysis of phenotypic pools in the first level screen. Marker positions were obtained from the microsatellite map distributed by the MIT mouse genome database. All SSLP markers colored in both black and gray are employed in the N2 analysis. Black markers represent a heterozygous (B6/CBA) and gray markers represent a homozygous (B6/B6) allele in the N2 male. Black SSLP markers representing heterozygous (B6/CBA) allele are used in the N3 mapping analysis.
|
|
View larger version (13K):
[in a new window]
|
Fig. 6. Interval mapping of the modifier locus in the N2 analysis. Chromosome 2 (A), chromosome 10 (B) and chromosome 18 (C). The vertical and horizontal axes display LOD scores and the relative positions of the markers along the chromosomes from centromere (left) to telomere (right) in cM, respectively (determined by QTL cartographer). Two broken horizontal lines depict the LOD scores (1.9 and 3.3), which represent suggestive and significant linkages (Lander and Kruglyak, 1995 ), respectively. Red lines represent values obtained from mutant embryos displaying phenotypes of no mandible, small mandible and normal mandible. The most likely position for each locus, determined by its two LOD support intervals, is indicated by the black bar above the plot (B,C).
|
|
View larger version (24K):
[in a new window]
|
Fig. 7. Interval mapping of the modifier locus in the N3 analysis on chromosome 2. The vertical and horizontal axes show LOD scores and the relative positions of the markers along the chromosomes from centromere (left) to telomere (right) in cM, respectively (determined by QTL cartographer). Two broken horizontal lines indicate the LOD scores (1.9 and 3.3), which represent suggestive and significant linkages (Lander and Kruglyak, 1995), respectively. The most likely position for each locus, determined by its two LOD support intervals, are indicated by the black bars above the plot.
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2002
