BackgroundResident macrophages regulate homeostatic and disease processes in multiple tissues, including the kidney. Despite having well defined markers to identify these cells in mice, technical limitations have prevented identification of a similar cell type across species. The inability to identify resident macrophage populations across species hinders the translation of data obtained from animal model to human patients.MethodsAs an entry point to determine novel markers that could identify resident macrophages across species, we performed single-cell RNA sequencing (scRNAseq) analysis of all T and B cell–negative CD45+ innate immune cells in mouse, rat, pig, and human kidney tissue.ResultsWe identified genes with enriched expression in mouse renal resident macrophages that were also present in candidate resident macrophage populations across species. Using the scRNAseq data, we defined a novel set of possible cell surface markers (Cd74 and Cd81) for these candidate kidney resident macrophages. We confirmed, using parabiosis and flow cytometry, that these proteins are indeed enriched in mouse resident macrophages. Flow cytometry data also indicated the existence of a defined population of innate immune cells in rat and human kidney tissue that coexpress CD74 and CD81, suggesting the presence of renal resident macrophages in multiple species.ConclusionsBased on transcriptional signatures, our data indicate that there is a conserved population of innate immune cells across multiple species that have been defined as resident macrophages in the mouse. Further, we identified potential cell surface markers to allow for future identification and characterization of this candidate resident macrophage population in mouse, rat, and pig translational studies.

To identify the role of the BBSome protein Bardet-Biedl syndrome 5 (BBS5) in photoreceptor function, protein trafficking, and structure using a congenital mutant mouse model. METHODS. Bbs5-/mice (2 and 9 months old) were used to assess retinal function and morphology. Hematoxylin and eosin staining of retinal sections was performed to visualize histology. Electroretinography was used to analyze rod and cone photoreceptor function. Retinal protein localization was visualized using immunofluorescence (IF) within retinal cryosections. TUNEL staining was used to quantify cell death. Transmission electron microscopy (TEM) was used to examine retinal ultrastructure. RESULTS. In the Bbs5-/retina, there was a significant loss of nuclei in the outer nuclear layer accompanied by an increase in cell death. Through electroretinography, Bbs5-/mice showed complete loss of cone photoreceptor function. IF revealed mislocalization of the cone-specific proteins M-and S-opsins, arrestin-4, CNGA3, and GNAT2, as well as a light-dependent arrestin-1 mislocalization, although perpherin-2 was properly localized. TEM revealed abnormal outer segment disk orientation in Bbs5-/-. CONCLUSIONS. Collectively, these data suggest that, although BBS5 is a core BBSome component expressed in all ciliated cells, its role within the retina mediates specific photoreceptor protein cargo transport. In the absence of BBS5, cone-specific protein mislocalization and a loss of cone photoreceptor function occur.

Primary cilia are critical sensory and signaling compartments present on most mammalian cell types. These specialized structures require a unique signaling protein composition relative to the rest of the cell to carry out their functions. Defects in ciliary structure and signaling result in a broad group of disorders collectively known as ciliopathies. One ciliopathy, Bardet-Biedl Syndrome (BBS; OMIM 209900), presents with diverse clinical features, many of which are attributed to defects in ciliary signaling during both embryonic development and postnatal life. For example, patients exhibit obesity, polydactyly, hypogonadism, developmental delay, and skeletal abnormalities along with sensory and cognitive deficits, but for many of these phenotypes it is uncertain which are developmental in origin. A subset of BBS proteins assembles into the BBSome complex, which is responsible for mediating transport of membrane proteins into and out of the cilium, establishing it as a sensory and signaling hub. Here we describe two new mouse models for BBS resulting from a congenital null and conditional allele of Bbs5. Bbs5 null mice develop a complex phenotype including craniofacial defects, skeletal shortening, ventriculomegaly, infertility, and pituitary anomalies. Utilizing the conditional allele, we show that the male fertility defects, ventriculomegaly, and pituitary abnormalities are only found when Bbs5 is mutated prior to P7 indicating a developmental origin. In contrast, mutation of Bbs5 results in obesity independent of the age of Bbs5 loss. Compared to other animal models of BBS, Bbs5 mutant mice exhibit pathologies that suggest a specialized role for Bbs5 in ciliary function.