Biology subjects

Little, K. A.

Publications and source records attributed to Little, K. A..

5 recordsLinked to original sources

bioRxiv2026

Dishevelled-mediated clustering stabilizes Frizzled6 and Vangl2 to establish planar cell polarity in the mammalian skin

Planar cell polarity (PCP) in epithelia is characterized by the polarized distribution of two opposing, membrane-associated PCP complexes across cell junctions. Transmembrane components of the PCP complex bridge cell junctions and organize into punctate, intercellular assemblies that exhibit a high degree of stability. Here, we define the contributions of the cytoplasmic PCP protein, Dishevelled (Dvl), in the sub-micron scale organization and stability of PCP complexes. Using endogenously-tagged fluorescent PCP reporters in the embryonic mouse epidermis, we quantify PCP protein mobility and clustering during polarization. We find that as transmembrane proteins immobilize into puncta, Dishevelled (Dvl2/3) co-accumulates with its transmembrane partner Frizzled (Fz6) in a polarized manner and stabilizes clusters of PCP complexes. We identify a previously unknown function for the oligomerizing DIX domain of Dvl3, typically associated with Wnt signaling, in Dvl3 asymmetric localization. These observations underscore a role for Dvl oligomerization in assembly and stabilization of asymmetric PCP puncta.

developmental biology↗

bioRxiv2025

A Conserved Domain of Cfap298 Governs Left-Right Symmetry Breaking in Vertebrates

Cfap298 is a highly conserved gene required for ciliary motility and dynein arm assembly. It plays a known role in Left-Right (LR) patterning in zebrafish and is linked to human ciliopathies. Here we describe a new Cfap298 mutant allele, Cfap298{Delta}3aa, which selectively interferes with LR axis establishment in mice. Mutant embryos display a range of laterality defects including situs solitus, situs inversus, and situs ambiguous, as indicated by abnormal heart, lung, and stomach positioning. At embryonic day 8.5, mutant embryos display abnormal Nodal, Pitx2, and Lefty1 expression patterns in the lateral plate mesoderm and midline, consistent with an early disruption in LR symmetry breaking. In mice, LR asymmetry is established by leftward fluid flow in the node, generated by planar-polarized cilia. Although cfap298 mutations are reported to affect cell polarity, we did not observe changes in cilia position, length, or planar cell polarity protein localization within the node, suggesting that Cfap298{Delta}3aafunctions at the level of cilia motility. Consistently, motile cilia lining the trachea of Cfap298{Delta}3aa mutants fail to beat. Expression of the Cfap298{Delta}3aa variant in zebrafish fails to rescue the LR defects of cfap298 (kurly) loss-of-function mutants. These results confirm that Cfap298 functions in LR axis formation in mammals and uncover a novel region of CFAP298 protein with a conserved and essential role in cilia motility. Summary StatementA novel Cfap298 mutation disrupts left-right patterning in mice by impairing ciliary motility, revealing a conserved protein region essential for this function across species.

developmental biology↗

bioRxiv2023

A Window into Mammalian Basement Membrane Development: Insights from the mTurq2-Col4a1 Mouse Model

Basement membranes (BMs) are specialized sheets of extracellular matrix that underlie epithelial and endothelial tissues. BMs regulate traffic of cells and molecules between compartments, and participate in signaling, cell migration and organogenesis. The dynamics of mammalian BMs, however, are poorly understood, largely due to a lack of models in which core BM components are endogenously labelled. Here, we describe the mTurquoise2-Col4a1 mouse, in which we fluorescently tag collagen IV, the main component of BMs. Using an innovative Planar-Sagittal live imaging technique to visualize the BM of developing skin, we directly observe BM deformation during hair follicle budding and basal progenitor cell divisions. The BMs inherent pliability enables dividing cells to remain attached to and deform the BM, rather than lose adhesion as generally thought. Using FRAP, we show BM collagen IV is extremely stable, even during periods of rapid epidermal growth. These findings demonstrate the utility of the mTurq2-Col4a1 mouse to shed new light on mammalian BM developmental dynamics.

cell biology↗

bioRxiv2021

Bacterial DNA on the skin surface overrepresents the viable skin microbiome

The skin microbiome provides vital contributions to human health. However, the spatial organization and viability of its bacterial components remain unclear. Here we apply culturing, imaging, and molecular approaches to human and mouse skin samples, and find that the skin surface is colonized by fewer viable bacteria than predicted by bacterial DNA levels. Instead, viable skin-associated bacteria are predominantly located in hair follicles and other cutaneous invaginations. Furthermore, we show that the skin microbiome has a uniquely low fraction of viable bacteria as compared to other human microbiome sites, indicating that most bacterial DNA on the skin surface is not associated with viable cells Additionally, a small number of bacterial families dominate each skin site and traditional sequencing methods overestimate both the richness and diversity of the skin microbiome. Finally, we performed an in-vivo skin microbiome perturbation-recovery study using human volunteers. Bacterial 16S rRNA gene sequencing revealed that, while the skin microbiome is remarkably stable even in the wake of aggressive perturbation, repopulation of the skin surface is driven by the underlying viable population. Our findings help explain the dynamics of skin microbiome perturbation, as bacterial DNA on the skin surface can be transiently perturbed but is replenished by a stable underlying viable population. These results address multiple outstanding questions in skin microbiome biology with significant implications for future efforts to study and manipulate it. Significance statementThis study provides a crucial update to the skin microbiome paradigm by showing that viable bacteria of the skin microbiome are primarily localized to hair follicles and other sub-cutaneous structures rather than the skin surface. The native distribution of skin-associated bacteria has not been previously evaluated, and here we show that the skin surface has few intact bacteria while deeper structures are replete with bacterial contents. We used orthogonal approaches to evaluate the source of bacterial DNA and the dynamics of bacterial repopulation on the skin surface to develop an updated model of the skin microbiome. By adjusting the current understanding of the skin microbiome to match this model, we will be able to address outstanding questions in the field.

microbiology↗

bioRxiv2020

Drawing the Borders of Olfactory Space

In studies of vision and audition, stimuli can be chosen to span the visible or audible spectrum; in olfaction, the axes and boundaries defining the analogous odorous space are unknown. As a result, the population of olfactory space is likewise unknown, and anecdotal estimates of 10,000 odorants have endured. The journey a molecule must take to reach olfactory receptors (OR) and produce an odor percept suggests some chemical criteria for odorants: a molecule must be 1) volatile enough to enter the air phase, 2) non-volatile and hydrophilic enough to sorb into the mucous layer coating the olfactory epithelium, 3) hydrophobic enough to enter an OR binding pocket, and 4) activate at least one OR. Here, we developed a simple and interpretable quantitative model that reliably predicts if a molecule is odorous or odorless based solely on the first three criteria. Applying our model to a database of all possible small organic molecules, we estimate that over 30 billion possible compounds are odorous, 6 orders of magnitude larger than current estimates of 10,000. With this model in hand, we can define the boundaries of olfactory space in terms of molecular volatility and hydrophobicity, enabling representative sampling of olfactory stimulus space.

neuroscience↗