May play a role in spermatogenesis (By similarity). May be involved in differentiation or function of ciliated cells. Interacts with alpha-tubulin. Localizes to the manchette in elongating spermatids (By similarity). Predominantly perinuclear in bronchial epithelial cells but also detected in the nucleus in some primary epithelial cells and in a number of cell lines. Expressed in epithelial cells of nasal polyps and in intact epithelium of bronchial biopsies from subjects with and without asthma. Strong expression in columnar cells with little or no expression in basal epithelial cells along the basement membrane. Strongly expressed in ciliated epithelial cells with lower levels in goblet cells (at protein level). Expressed during in vitro differentiation of bronchial epithelial cells. In fetal lung, expression is barely detectable at 10 weeks post-conception but is strong in airway epithelium at 12.3 weeks post-conception. Down-regulated by IL13. Belongs to the SMRP1 family.