msi is required in spermatocytes for correct meiotic chromosome segregation and cytokinesis.

RNAi generated by PCR using primers directed to this gene causes a cell growth and viability phenotype when assayed in Kc167 and S2R⁺ cells.

msi protein acts as a translational repressor of ttk in the neuronal lineage, acting in the 3' untranslated region of the ttk mRNA. N signalling does not affect msi expression, though msi can act downstream of N, therefore N signalling is more likely to regulate msi activity than its expression.

msi is epistatic to N during the asymmetric cell division giving rise to external sensory organ precursor IIa and IIb cells.

msi functions to regulate ttk expression.

msi and sina function redundantly in R1 and R6 to down-regulate ttk in the developing photoreceptor cells.

msi is required for the development of adult external sensory organs (sensilla). msi mutation typically results in extra sockets and/or shafts. It is suggested that the msi phenotype results from transformation of a neuron/glial-precursor cell into a second shaft/socket-precursor cell. It is proposed that the msi protein regulates sensillum development by controlling the expression of target genes at the post-transcriptional level.

msi is required for development of adult external sensory organs (sensilla). Mutations in msi result in the appearance of extra outer support cells. It is proposed that the msi protein regulates sensillum development by controlling the expression of target genes at the posttranscriptional level.