Different neuroendocrine cell types in thepars intercerebralisofPeriplaneta americanaproduce their own specific IGF-related peptides

Abstract

Of the nine genes of the American cockroach, Periplaneta americana, coding for peptides related to insulin and insulin-like growth factor, seven show significant expression in the central nervous system as demonstrated by the polymerase chain reaction on reverse transcribed RNA. In situ hybridisation shows that five of those are expressed by cells in the pars intercerebralis. Antisera raised to the predicted peptides show that these cells are neuroendocrine in nature and project to the corpora cardiaca. Interestingly, and in contrast to Drosophila where a single cell type expresses a number of genes expressing several such peptides, there are at least three cell types that each express different genes. Whereas in Drosophila the neuroendocrine cells producing insulin-like peptides also express sulfakinins, the arthropod orthologs of gastrin and cholecystokinin, in Periplaneta the sulfakinins are produced by different cells. Other neuropeptides known to be produced by the pars intercerebralis in this and other insect species, such as the CRF-like diuretic hormone, neuroparsin, leucokinin or myosuppressin, neither colocalize with an insulin-related peptide. The differential expression of these peptides and the existence of multiple insulin receptors in this species implies a more complex regulation by insulin and IGF-related peptides in cockroaches than in the fruit fly.

Differential expression of some termite neuropeptides and insulin/IGF-related hormones and their plausible functions in growth, reproduction and caste determination

“…As there is no ovary tissue in the head the expression of brovirpin in the head is likely by neuroendocrine cells in the brain. Such a dual expression of a sirp by both the ovary and brain neuroendocrine cells is also observed in the case of Periplaneta sirp 3 (Veenstra, 2023). Brovirpin is also expressed in much larger quantities in female than in male soldiers in Z. nevadensis (Suppl.…”

“…Spreadsheet-1). The reads for birpin, cirpin and brovirpin in SRAs from heads or heads and thoraces and the presence of characteristic endocrine convertase cleavages sites in their precursors suggests that these sirps are likely expressed by brain neuroendocrine cells, as is the case for such peptides in other insect species, including the American and German cockroaches (Castro-Arnau et al, 2019;Veenstra, 2023). However, unlike birpin and cirpin, brovirpin is also expressed in the abdomen.…”

“…In all these species there is a single neuroendocrine cell type in the brain that produce one or more sirps. This may well be different in termites, as preliminary results in the American cockroach reveal that in that species at least three different neuroendocrine cell types each produce their own specific sirps (Veenstra, 2023).…”