Hypomorphic mutation in hnRNP U results in post-implantation lethality

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Heterogeneous ribonuclear protein U (hnRNP U) is crucial for various cellular processes.
• Gene mutations can lead to developmental abnormalities and embryonic lethality.
• Gene trap retroviruses are tools for identifying gene function through insertional mutagenesis.

Purpose of the Study:

• To characterize the function of hnRNP U during mouse embryonic development.
• To investigate the consequences of a hypomorphic mutation in the Hnrnpu gene.
• To determine the expression levels of hnRNP U required for embryonic viability.

Main Methods:

• Generation of a gene trap mouse model by retroviral insertion into the Hnrnpu gene.
• Analysis of embryonic development in homozygous mutant mice.
• Assessment of hnRNP U transcript levels in mutant cell lines using quantitative methods.

Main Results:

• Homozygous Hnrnpu mutant embryos exhibited developmental abnormalities by embryonic day 6.5 (E6.5) and were resorbed by E10.5.
• The retroviral insertion resulted in alternative splicing, creating a hypomorphic mutation with reduced hnRNP U expression.
• Mutant cell lines displayed 2- to 5-fold lower hnRNP U transcript levels compared to wild-type.

Conclusions:

• hnRNP U is essential for mouse embryonic development, with near wild-type levels required for viability.
• Disruption of Hnrnpu gene function through insertional mutagenesis leads to embryonic lethality.
• This study highlights the critical role of hnRNP U in early embryogenesis.