Early stages of induction of anterior head ectodermal properties in Xenopus embryos are mediated by transcriptional cofactor ldb1

Whole‑exome sequencing analysis of products of conception identifies novel mutations associated with missed abortion

Missed abortion (MA) refers to a pregnancy in which there is fetal demise without outside intervention, and additionally no uterine activity that may expel the product of conception (POC) prior to 20 weeks of gestation. Chromosomal abnormalities are the primary cause of MA and single gene defects in the POC may additionally be associated with MA; however, few studies have been conducted on the identification of mutations by whole-exome sequencing. In the present study, 19 unrelated MA POCs were collected and whole-exome sequencing was performed on the POC. Bioinformatics analysis was performed on sequence variants from a list of 286 selected candidate genes that were associated with early embryonic lethality and MA. A total of 36 sequence variants in 32 genes potentially associated with MA were identified in 15 out of 19 patients. Gene Ontology analysis suggested that these genes were enriched in biological processes in early embryonic development, including ‘chordate embryonic development’, ‘cell proliferation’ and ‘forebrain development’. Further strict in silico bioinformatics analysis predicted that the LIM domain-binding protein 1 (c.662C>T; p.S221L) variant was a highly pathogenic variant. In conclusion, the results of the present study provide researchers and clinicians with a better understanding of the etiology and molecular mechanism of human embryonic lethality and MA.

Functional Cloning Using a Xenopus Oocyte Expression System

Identification of genes responsible for embryonic induction poses a number of challenges; to name a few, secreted molecules of interest may be low in abundance, may not be secreted but tethered to the signaling cell(s), or may require the presence of binding partners or upstream regulatory molecules. Thus in a search for gene products capable of eliciting an early lens-inductive response in competent ectoderm, we utilized an expression cloning system that would allow identification of paracrine or juxtacrine factors as well as transcriptional or other regulatory proteins. Pools of mRNA were injected into Xenopus oocytes, and responding tissue placed directly on the oocytes and co-cultured. Following functional cloning of ldb1 from a neural plate stage cDNA library based on its ability to elicit the expression of the early lens placode marker foxe3 in lens-competent animal cap ectoderm, we characterized the mRNA expression pattern, and assayed developmental progression following overexpression or knockdown of ldb1. This system is suitable in a very wide variety of contexts where identification of an inducer or its upstream regulatory molecules is sought using a functional response in competent tissue.