Early‐onset aging and mitochondrial defects associated with loss of histone acetyltransferase 1 (Hat1)

Histone acetyltransferase 1 (Hat1) is responsible for the acetylation of newly synthesized histone H4 on lysines 5 and 12 during the process of chromatin assembly. To understand the broader biological role of Hat1, we have generated a conditional mouse knockout model of this enzyme. We previously reported that Hat1 is required for viability and important for mammalian development and genome stability. In this study, we show that haploinsufficiency of Hat1 results in a significant decrease in lifespan. Defects observed in Hat1^+/? mice are consistent with an early‐onset aging phenotype. These include lordokyphosis (hunchback), muscle atrophy, minor growth retardation, reduced subcutaneous fat, cancer, and paralysis. In addition, the expression of Hat1 is linked to the normal aging process as Hat1 mRNA and protein becomes undetectable in many tissues in old mice. At the cellular level, fibroblasts from Hat1 haploinsufficient embryos undergo early senescence and accumulate high levels of p21. Hat1^+/? mouse embryonic fibroblasts (MEFs) display modest increases in endogenous DNA damage but have significantly higher levels of reactive oxygen species (ROS). Consistently, further studies show that Hat1^?/? MEFs exhibit mitochondrial defects suggesting a critical role for Hat1 in mitochondrial function. Taken together, these data show that loss of Hat1 induces multiple hallmarks of early‐onset aging.     

Prediction of structural consequences for disease causing variants in C21orf2 protein using computational approaches

Amyotrophic lateral sclerosis (ALS), a progressive motor-neurone disease, affects individuals usually aged between 50 and 70 years. C21orf2, recently identified as the new ALS susceptibility gene, harbours rare missense mutations that cause this fatal disease. We used bioinformatics and molecular modelling approaches to study specific ALS-associated mutations in C21orf2. Both native and mutant structures of the protein obtained from homology modelling were analysed in detail to gain insights into the potential impact of these mutations on the protein structure and its function. Our analyses reveal that more than 75% of the mutations are likely to be deleterious. These effects seem to carry through to mouse C21orf2 as well, indicating that mouse would make a viable animal model to study this ALS gene in detail.     

Exploring the post-transcriptional RNA world with DNA microarrays

Genomic approaches are valuable for understanding the complex layer of gene regulation that involves the control of RNA processing, localization and stability. Recent work provides a prime example of the power of unbiased microarray-based methods to discover unexpected functions for proteins in the RNA world. The challenges ahead relate to extending such approaches to larger genomes and to integrating this type of information with that generated by standard expression profiling.