CRISPR disruption of TCTP gene impaired normal development in the silkworm Bombyx mori.

The translationally controlled tumor protein (TCTP) is a highly conserved and multifunctional protein with activities ranging from cytoskeletal regulation to transcription regulation in numerous organisms. In insects, TCTP is essential for cell growth and proliferation. Recently, TCTP has been reported to affect the innate intestinal immune pathway in the Bombyx mori silkworm, a lepidopteran model insect. However, the comprehensive physiological roles of TCTP in the silkworm remain poorly understood. Here, we performed functional analysis of BmTCTP by using a binary transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeat/RNA-guided CRISPER-associated protein 9 nucleases) system. Disruption of BmTCTP led to developmental arrestment and subsequent lethality in third instar larvae. Histological analysis revealed that growth impairment originated from decreased cell size, and the proliferation and differentiation of intestinal epithelial cells were also affected. RNA-seq analysis revealed that genes involved in carbohydrate metabolism, lipid metabolism and digestive system pathways were significantly affected by BmTCTP depletion. Together, the results demonstrated that BmTCTP plays a key role in controlling larval growth and development.