The Na(+)/Ca(2+) exchanger NCKX4 governs termination and adaptation of the mammalian olfactory response

Sensory perception requires accurate encoding of stimulus information by sensory receptor cells. We identified NCKX4, a potassium-dependent Na(+)/Ca(2+) exchanger, as being necessary for rapid response termination and proper adaptation of vertebrate olfactory sensory neurons (OSNs). Nckx4(-/-) (also known as Slc24a4) mouse OSNs displayed substantially prolonged responses and stronger adaptation. Single-cell electrophysiological analyses revealed that the majority of Na(+)-dependent Ca(2+) exchange in OSNs relevant to sensory transduction is a result of NCKX4 and that Nckx4(-/-) mouse OSNs are deficient in encoding action potentials on repeated stimulation. Olfactory-specific Nckx4(-/-) mice had lower body weights and a reduced ability to locate an odorous source. These results establish the role of NCKX4 in shaping olfactory responses and suggest that rapid response termination and proper adaptation of peripheral sensory receptor cells tune the sensory system for optimal perception

A Recent Class of Chemosensory Neurons Developed in Mouse and Rat

In most animal species, the vomeronasal organ ensures the individual recognition of conspecifics, a prerequisite for a successful reproduction. The vomeronasal organ expresses several receptors for pheromone detection. Mouse vomeronasal type-2 receptors (V2Rs) are restricted to the basal neurons of this organ and organized in four families. Family-A, B and D (family ABD) V2Rs are expressed monogenically (one receptor per neuron) and coexpress with either Vmn2r1 or Vmn2r2, two members of family-C V2Rs. Thus, basal neurons are characterized by specific combinations of two V2Rs. To investigate this issue, we raised antibodies against all family-C V2Rs and analyzed their expression pattern. We found that six out of seven family-C V2Rs (Vmn2r2-7) largely coexpressed and that none of the anti-Vmn2r2-7 antibodies significantly stained Vmn2r1 positive neurons. Thus, basal neurons are divided into two complementary subsets. The first subset (Vmn2r1-positive) preferentially coexpresses a distinct group of family-ABD V2Rs, whereas the second subset (Vmn2r2-7-positive) coexpresses the remaining group of V2Rs. Phylogenetic reconstruction and the analysis of genetic loci in various species reveal that receptors expressed by this second neuronal subset are recent branches of the V2R tree exclusively present in mouse and rat. Conversely, V2Rs expressed in Vmn2r1 positive neurons, are phylogenetically ancient and found in most vertebrates including rodents. Noticeably, the more recent neuronal subset expresses a type of Major Histocompatibility Complex genes only found in murine species. These results indicate that the expansion of the V2R repertoire in a murine ancestor occurred with the establishment of a new population of vomeronasal neurons in which coexists the polygenic expression of a recent group of family-C V2Rs (Vmn2r2-7) and the monogenic expression of a recent group of family-ABD V2Rs. This evolutionary innovation could provide a molecular rationale for the exquisite ability in individual recognition and mate choice of murine species

To be suddenly White: Realism and the problem of agency in United States passing narratives

Chapter one provides a historical and critical overview of passing and the three ethnic groups discussed in the dissertation: African Americans, Italian Americans, and Jewish Americans. Chapter two offers readings of Frances E. W. Harper\u27s Iola Leroy and William Dean Howells\u27s An Imperative Duty—both of which are taken to be early examples of realist passing narratives. The chapter concludes that—vis-à-vis Howells\u27s own standards for realism—Harper\u27s text succeeds politically, if not always aesthetically, in ways Howells\u27s text does not. Chapter three focuses upon “white ethnic” male-centered texts, first distinguishing between acculturation narratives (by Abraham Cahan, Giuseppe Cautela, and Garibaldi LaPolla) and passing narratives, and then providing readings of two passing narratives (by Ludwig Lewisohn and Guido d\u27Agostino). In the final analysis, passing is viewed as not only a cultural violation, but in some ways, a biological impossibility—a testament to the racialism of many European/American immigrant narratives. Chapter four traces the history of the male-centered African/American passing narrative from 1899 to 1931. The texts written in this time period—by Charles Chesnutt, James Weldon Johnson, and George Schuyler—reveal a greater tendency than their “white ethnic”-authored counterparts to critique race as an idea and to employ irony, even full-blown satire, as a weapon against harmful racial ideologies. Chapter five examines the trope of passing in ethnic female-centered narratives by Mary Antin, Anzia Yezierska, and Helen Barolini. In each, the complicating factor of female gender is part and parcel of the protagonists\u27 passing strategies and the problematic agency they suggest. Also in these texts, passing is rejected either as an unstated impossibility or as culturally undesirable. Chapter six concludes the study by tracing the palpable move toward modernism found in African/American female-centered passing narratives published between 1899 and 1929 by Chesnutt, Walter White, Jessie Redmon Fauset, and Nella Larsen. Beginning with the melodramatic realism of the 1890s and moving to the purer social realism of the 1920s, and then, finally, to the near-existential modernism of Passing (1929), it becomes clear that the explicitly stated determinisms of race and gender create the need for less traditional modes of representation