Retinoic Acid Controls the Bilateral Symmetry of Somite Formation in the Mouse Embryo

A striking characteristic of vertebrate embryos is their bilaterally symmetric body plan, which is particularly obvious at the level of the somites and their derivatives such as the vertebral column. Segmentation of the presomitic mesoderm must therefore be tightly coordinated along the left and right embryonic sides. We show that mutant mice defective for retinoic acid synthesis exhibit delayed somite formation on the right side. Asymmetric somite formation correlates with a left-right desynchronization of the segmentation clock oscillations. These data implicate retinoic acid as an endogenous signal that maintains the bilateral synchrony of mesoderm segmentation, and therefore controls bilateral symmetry, in vertebrate embryos

Additional file 2: Figure S2. of Variant mapping and mutation discovery in inbred mice using next-generation sequencing

TUNEL analysis of 8 fields each from liver samples from E18.5 wild-type and J327 mice reveal a modest but highly significant increase in apoptosis in the mutant (p = 7.06E-05). (PDF 21 kb

Additional file 1: Figure S1. of Variant mapping and mutation discovery in inbred mice using next-generation sequencing

Sequence analysis of transcripts from K416 mutant mice reveals a mixed population that includes wild-type and mutant versions carrying a 4 base pair insertion that changes the frame and results in premature termination. (PDF 38 kb

Improvement of ENU Mutagenesis Efficiency Using Serial Injection and Mismatch Repair Deficiency Mice

<div><p>ENU mutagenesis is a powerful method for generating novel lines of mice that are informative with respect to both fundamental biological processes and human disease. Rapid developments in genomic technology have made the task of identifying causal mutations by positional cloning remarkably efficient. One limitation of this approach remains the mutation frequency achievable using standard treatment protocols, which currently generate approximately 1–2 sequence changes per megabase when optimized. In this study we used two strategies to attempt to increase the number of mutations induced by ENU treatment. One approach employed mice carrying a mutation in the DNA repair enzyme <i>Msh6</i>. The second strategy involved injection of ENU to successive generations of mice. To evaluate the number of ENU-induced mutations, single mice or pooled samples were analyzed using whole exome sequencing. The results showed that there is considerable variability in the induced mutation frequency using these approaches, but an overall increase in ENU-induced variants from one generation to another was observed. The analysis of the mice deficient for <i>Msh6</i> also showed an increase in the ENU-induced variants compared to the wild-type ENU-treated mice. However, in both cases the increase in ENU-induced mutation frequency was modest.</p></div

Fertility after ENU treatment.

<p>Fertility after ENU treatment.</p

Variant analysis for individual mice.

<p>Variant analysis for individual mice.</p

Variant analysis for pooled mice.

<p>Variant analysis for pooled mice.</p

Effect of ENU treatment on survival.

<p><i>Msh6</i>^<i>+/-</i> males show survival comparable to wild-type males after treatment with the standard concentration of ENU (90mg/kg x 3). Survival of ENU-treated <i>Msh6</i>^<i>-/-</i>males is much reduced. Death is expressed in days.</p

Distribution of ENU-induced mutations in A-T vs. G-C base-pairs.

<p>Distribution of ENU-induced mutations in A-T vs. G-C base-pairs.</p

Breeding scheme for analysis of serial ENU-treatment in wild-type and MMR defective mice.

<p>G01 males carry a random set of <i>de novo</i> point mutations induced by ENU treatment of wild-type or MMR-mutant G0 mice. G02, G03 and G04 carry mutations that were induced in their respective parents, as well as those inherited from previous generations. Each generation treated with ENU will on average have 3000–6000 new ENU-induced variants genome wide. After ENU treatment each male is crossed with a wild-type female; their progeny will inherit newly induced mutations and 50% of those of the parent. The mutations are sampled by exome analysis; the expected number of ascertained mutations (E) is shown. The ENU treatment was performed on three successive generations for the <i>Msh6</i>^<i>+/+</i> mice and four generation for the <i>Msh6</i>^<i>+/-</i> mice. <i>Msh6</i>^<i>-/-</i> mice did not tolerate ENU treatment.</p