On the tear proteome of the house mouse (Mus musculus musculus) in relation to chemical signalling

Mammalian tears are produced by lacrimal glands to protect eyes and may function in chemical communication and immunity. Recent studies on the house mouse chemical signalling revealed that major urinary proteins (MUPs) are not individually unique in Mus musculus musculus. This fact stimulated us to look for other sexually dimorphic proteins that may—in combination with MUPs—contribute to a pool of chemical signals in tears. MUPs and other lipocalins including odorant binding proteins (OBPs) have the capacity to selectively transport volatile organic compounds (VOCs) in their eight-stranded beta barrel, thus we have generated the tear proteome of the house mouse to detect a wider pool of proteins that may be involved in chemical signalling. We have detected significant male-biased (7.8%) and female-biased (7%) proteins in tears. Those proteins that showed the most elevated sexual dimorphisms were highly expressed and belong to MUP, OBP, ESP (i.e., exocrine gland-secreted peptides), and SCGB/ABP (i.e., secretoglobin) families. Thus, tears may have the potential to elicit sex-specific signals in combination by different proteins. Some tear lipocalins are not sexually dimorphic—with MUP20/darcin and OBP6 being good examples—and because all proteins may flow with tears through nasolacrimal ducts to nasal and oral cavities we suggest that their roles are wider than originally thought. Also, we have also detected several sexually dimorphic bactericidal proteins, thus further supporting an idea that males and females may have adopted alternative strategies in controlling microbiota thus yielding different VOC profiles.

Myb permits multilineage airway epithelial cell differentiation

The epithelium of the pulmonary airway is specially differentiated to provide defense against environmental insults, but also subject to dysregulated differentiation that results in lung disease. The current paradigm for airway epithelial differentiation is a one-step program whereby a p63(+) basal epithelial progenitor cell generates a ciliated or secretory cell lineage, but the cue for this transition and whether there are intermediate steps are poorly defined. Here, we identify transcription factor Myb as a key regulator that permits early multilineage differentiation of airway epithelial cells. Myb(+) cells were identified as p63(-) and therefore distinct from basal progenitor cells, but were still negative for markers of differentiation. Myb RNAi treatment of primary-culture airway epithelial cells and Myb gene deletion in mice resulted in a p63(-) population with failed maturation of Foxj1(+) ciliated cells as well as Scbg1a1(+) and Muc5ac(+) secretory cells. Consistent with these findings, analysis of whole genome expression of Myb-deficient cells identified Myb-dependent programs for ciliated and secretory cell differentiation. Myb(+) cells were rare in human airways but were increased in regions of ciliated cells and mucous cell hyperplasia in samples from subjects with chronic obstructive pulmonary disease. Together, the results show that a p63(-) Myb(+) population of airway epithelial cells represents a distinct intermediate stage of differentiation that is required under normal conditions and may be heightened in airway disease.

Estrogen-regulated transcription of the uteroglobin gene from the brown hare (Lepus capensis)

To get further insights on the estrogen regulation of the uteroglobin (UG) gene, the 5'-flanking region of the UG gene from the brown hare (Lepus capensis) (Lc) was cloned and compared with those from two phylogenetically related species: the rabbit (Orictolagus cuniculus) (Oc) and the volcano rabbit (Romerolagus diazi) (Rd). The Lc-UG gene is very similar to those from rabbits (94%) and volcano rabbits (95%), and shares a number of genetic elements, including an estrogen response element (ERE). The estrogen-regulated transcription of a series of progressive 5'-deletion mutants of the Lc-UG gene, identified a functional ERE in the promoter region exhibiting the same orientation and relative position than that previously described in rabbits. The Lc-ERE is identical to the Oc-ERE, but different from both the Rd-ERE and the consensus ERE (c-ERE) by one nucleotide. We also detected important species-specific differences in the estrogen-regulated transcription of the UG gene. A luciferase reporter driven by 333 base pairs (bp) of the Lc-UG promoter elicited a higher response to estradiol than its related counterparts when expressed in estrogen-sensitive MCF-7 cells. Several ERE-like motifs which failed to act as functional EREs were also identified; one of them exhibited two mismatches in its palindromic sequence, a characteristic exhibited in many other natural occurring EREs, including the Rd-ERE.