How do histone modifications contribute to transgenerational epigenetic inheritance in C. elegans?

Gene regulatory information can be inherited between generations in a phenomenon termed transgenerational epigenetic inheritance (TEI). While examples of TEI in many animals accumulate, the nematode Caenorhabditis elegans has proven particularly useful in investigating the underlying molecular mechanisms of this phenomenon. In C. elegans and other animals, the modification of histone proteins has emerged as a potential carrier and effector of transgenerational epigenetic information. In this review, we explore the contribution of histone modifications to TEI in C. elegans. We describe the role of repressive histone marks, histone methyltransferases, and associated chromatin factors in heritable gene silencing, and discuss recent developments and unanswered questions in how these factors integrate with other known TEI mechanisms. We also review the transgenerational effects of the manipulation of histone modifications on germline health and longevity.

Marketing strategies used for alternative protein products sold in Australian supermarkets in 2014, 2017, and 2021.

Introduction: Marketing plays an important role in consumers' perceptions and acceptance of new foods. The purpose of this study was to investigate the marketing strategies used for alternative protein products available in Australia in 2014, 2017, and 2021. Methods: Product data were extracted from FoodTrack™, an established database of packaged supermarket products. Marketing strategies investigated included product format descriptors, front of pack (FOP) labeling claims, price, and in-store placement (2021 only). Results: Data from 292 alternative protein products (n = 12 tofu-based products; n = 100 legume-based products; and n = 180 plant-based meats) were analyzed. Across the product range, "burgers" (n = 86), "strips and similar" (n = 51) and "sausages" (n = 42) were the most common product formats, accounting for ∼61% of the product range. Nutrient content claims featured on 273 (93%) products. "Positive" nutrient claims (those highlighting the presence of a nutrient) occurred on FOP labels four times more than "negative" nutrient claims (those highlighting the absence or low levels of a nutrient; 432 versus 101, respectively). Protein-related claims were the most common "positive" nutrient claim (n = 180, 62%). Health claims on FOP labels appeared on 10% of products. Most products (n = 265, 91%) mentioned a dietary pattern (such as "vegetarian" and "plant-based"), or a combination of dietary patterns on their FOP label. The price of alternative products increased over time; between 2014 and 2021, on average, the unit price increased (9% increase, p = 0.035) and the pack size decreased (14% decrease, p < 0.001). There was inconsistency in product placement across the eight stores visited. Occasionally (n = 3 of 13 locations), chilled alternative protein products were positioned near conventional meat products. More commonly, alternative protein products shared space with other vegetarian products (such as non-dairy cheeses and tofu blocks) or alongside convenience products, suggesting these products are promoted as convenience foods, or options for individuals with special dietary needs. Discussion: This study provides a useful evidence base to understand the marketing strategies used for alternative protein products. It appears from this analysis that considerable effort has gone into providing consumers with a level of familiarity and comfort prior to purchasing these alternative protein products.

Mitochondrial succinate dehydrogenase function is essential for sperm motility and male fertility.

Mitochondrial health is crucial to sperm quality and male fertility, but the precise role of mitochondria in sperm function remains unclear. SDHA is a component of the succinate dehydrogenase (SDH) complex and plays a critical role in mitochondria. In humans, SDH activity is positively correlated with sperm quality, and mutations in SDHA are associated with Leigh Syndrome. Here we report that the C. elegans SDHA orthologue SDHA-2 is essential for male fertility: sdha-2 mutants produce dramatically fewer offspring due to defective sperm activation and motility, have hyperfused sperm mitochondria, and disrupted redox balance. Similar sperm motility defects in sdha-1 and icl-1 mutant animals suggest an imbalance in metabolites may underlie the fertility defect. Our results demonstrate a role for SDHA-2 in sperm motility and male reproductive health and establish an animal model of SDH deficiency-associated infertility.

Transgenerational Epigenetic Inheritance Is Revealed as a Multi-step Process by Studies of the SET-Domain Proteins SET-25 and SET-32.

It is now clear that heredity is not determined purely by Mendelian genetic inheritance; sometimes, epigenetic signals can be passed from parent to progeny for multiple generations. This phenomenon is termed transgenerational epigenetic inheritance (TEI), and examples have now been observed in multiple organisms including plants, flies, mice, and nematodes. Here we discuss the recent findings that TEI is a multi-step process and that the putative chromatin modifiers SET-25 and SET-32 are important in the establishment but not maintenance of silencing.

Chromatin Modifiers SET-25 and SET-32 Are Required for Establishment but Not Long-Term Maintenance of Transgenerational Epigenetic Inheritance.

Some epigenetic modifications are inherited from one generation to the next, providing a potential mechanism for the inheritance of environmentally acquired traits. Transgenerational inheritance of RNAi phenotypes in Caenorhabditis elegans provides an excellent model to study this phenomenon, and although studies have implicated both chromatin modifications and small RNA pathways in heritable silencing, their relative contributions remain unclear. Here, we demonstrate that the putative histone methyltransferases SET-25 and SET-32 are required for establishment of a transgenerational silencing signal but not for long-term maintenance of this signal between subsequent generations, suggesting that transgenerational epigenetic inheritance is a multi-step process with distinct genetic requirements for establishment and maintenance of heritable silencing. Furthermore, small RNA sequencing reveals that the abundance of secondary siRNAs (thought to be the effector molecules of heritable silencing) does not correlate with silencing phenotypes. Together, our results suggest that the current mechanistic models of epigenetic inheritance are incomplete.