Examining How Ribosomal Proteins Affect Growth And Body Size

Abstract

Adequate amounts of nutrients are important for growth and development. Ingested nutrients are used for processes that meet the metabolic needs of the body allowing for growth and development. An important aspect of growth is ribosome biogenesis. The ribosome is the molecular machine that is responsible for protein synthesis, hence growth. However, what still remains unclear is the contribution of rRNA and ribosomal proteins to tissue and body growth in developing animals. The aim of this project was to study the role of certain ribosomal proteins in growth and development using Drosophila. Drosophila is a powerful genetic model system to study cell and organismal responses to growth cues. Over a 4-day period, Drosophila larvae can grow over 200 fold in mass in response to nutrient availability. For this project a class of Drosophila mutants known as Minutes were studied. These flies harbored mutations in different ribosomal proteins. These flies are lethal as homozygous mutants, however as heterozygotes with reduced levels of ribosome and protein synthesis, they have a characteristic slow rate of development.  The experiments conducted showed that mutations in certain ribosomal proteins result in no change or an increase in overall body size of Drosophila pupae in comparison to control. The results showed a link to delayed development to the pupal stage, suggesting an explanation to the increased body size. These results also showed a possible link of some ribosomal proteins functioning as tumor suppressors where suppressed expression results in increased overall body growth. These findings showed a striking contrast to the hypothesized decrease in overall growth from decreased ribosome synthesis, opening the door to numerous questions regarding the molecular mechanism of ribosomal proteins.