Microglial Pten safeguards postnatal integrity of the cortex and sociability.

Microglial abnormalities may contribute to neurodevelopmental disorders. PTEN is implicated as a susceptibility gene for autism spectrum disorders and its germline ablation in mice causes behavioral abnormalities. Here we find postnatal PTEN deletion in microglia causes deficits in sociability and novel object recognition test. Mutant mice harbor markedly more activated microglia that manifest enhanced phagocytosis. Interestingly, two-week postponement of microglia PTEN ablation leads to no social interaction defects, even though mutant microglia remain abnormal in adult animals. Disturbed neurodevelopment caused by early PTEN deletion in microglia is characterized by insufficient VGLUT1 protein in synaptosomes, likely a consequence of enhanced removal by microglia. In correlation, in vitro acute slice recordings demonstrate weakened synaptic inputs to layer 5 pyramidal neurons in the developing cortex. Therefore, microglial PTEN safeguards integrity of neural substrates underlying sociability in a developmentally determined manner.

A GPR174-CCL21 module imparts sexual dimorphism to humoral immunity.

Humoral immune responses to immunization and infection and susceptibilities to antibody-mediated autoimmunity are generally lower in males1-3. However, the mechanisms underlying such sexual dimorphism are not well understood. Here we show that there are intrinsic differences between the B cells that produce germinal centres in male and female mice. We find that antigen-activated male B cells do not position themselves as efficiently as female B cells in the centre of follicles in secondary lymphoid organs, in which germinal centres normally develop. Moreover, GPR174-an X-chromosome-encoded G-protein-coupled receptor-suppresses the formation of germinal centres in male, but not female, mice. This effect is intrinsic to B cells, and correlates with the GPR174-enhanced positioning of B cells towards the T-cell-B-cell border of follicles, and the distraction of male, but not female, B cells from S1PR2-driven follicle-centre localization. Biochemical fractionation of conditioned media that induce B-cell migration in a GPR174-dependent manner identifies CCL21 as a GPR174 ligand. In response to CCL21, GPR174 triggers a calcium flux and preferentially induces the migration of male B cells; GPR174 also becomes associated with more Gαi protein in male than in female B cells. Male B cells from orchidectomized mice exhibit impaired GPR174-mediated migration to CCL21, and testosterone treatment rescues this defect. Female B cells from testosterone-treated mice exhibit male-like GPR174-Gαi association and GPR174-mediated migration. Deleting GPR174 from male B cells causes more efficient positioning towards the follicular centre, the formation of more germinal centres and an increased susceptibility to B-cell-dependent experimental autoimmune encephalomyelitis. By identifying GPR174 as a receptor for CCL21 and demonstrating its sex-dependent control of B-cell positioning and participation in germinal centres, we have revealed a mechanism by which B-cell physiology is fine-tuned to impart sexual dimorphism to humoral immunity.

Chemical synthesis of a two-photon-activatable chemokine and photon-guided lymphocyte migration in vivo.

Chemokine-guided lymphocyte positioning in tissues is crucial for normal operation of the immune system. Direct, real-time manipulation and measurement of single-cell responses to chemokines is highly desired for investigating the cell biology of lymphocyte migration in vivo. Here we report the development of the first two-photon-activatable chemokine CCL5 through efficient one-pot total chemical synthesis in milligram scale. By spatiotemporally controlled photoactivation, we show at the single-cell level that T cells perceive the directional cue without relying on PI3K activities, which are nonetheless required for persistent migration over an extended period of time. By intravital imaging, we demonstrate artificial T-cell positioning in cutaneous tissues and lymph nodes. This work establishes a general strategy to develop high-quality photo-activatable protein agents through tailor-designed caging of multiple residues and highlights the potential of photo-activatable chemokines for understanding and potential therapeutic manipulation of cell positioning and position-controlled cell behaviours in vivo.

Nuclear receptors of the NR4a family are not required for the development and function of follicular T helper cells.

Follicular T helper (Tfh) cells promote germinal center (GC) reaction and high-affinity antibody production. The molecular mechanisms that regulate development and function of Tfh cells are not fully understood. Here we report that ligand-independent nuclear receptors of the Nr4a family are highly expressed in Tfh cells. In a well-established adoptive transfer model, enforced expression of Nr4a receptors reduces helper T cell expansion but apparently increased the T cell capacity to promote the GC response. On the other hand, deletion of all Nr4a receptors in T cells did not significantly affect expansion or differentiation of Tfh cells or the development of GC reaction. These findings suggest that Nr4a receptors may promote but are not necessary for Tfh development or function in vivo.