Sex Differences in the Brain: A Whole Body Perspective

Most writing on sexual differentiation of the mammalian brain (including our own) considers just two organs: the gonads and the brain. This perspective, which leaves out all other body parts, misleads us in several ways. First, there is accumulating evidence that all organs are sexually differentiated, and that sex differences in peripheral organs affect the brain. We demonstrate this by reviewing examples involving sex differences in muscles, adipose tissue, the liver, immune system, gut, kidneys, bladder, and placenta that affect the nervous system and behavior. The second consequence of ignoring other organs when considering neural sex differences is that we are likely to miss the fact that some brain sex differences develop to compensate for differences in the internal environment (i.e., because male and female brains operate in different bodies, sex differences are required to make output/function more similar in the two sexes). We also consider evidence that sex differences in sensory systems cause male and female brains to perceive different information about the world; the two sexes are also perceived by the world differently and therefore exposed to differences in experience via treatment by others. Although the topic of sex differences in the brain is often seen as much more emotionally charged than studies of sex differences in other organs, the dichotomy is largely false. By putting the brain firmly back in the body, sex differences in the brain are predictable and can be more completely understood

Neuropoietin, a new IL-6-related cytokine signaling through the ciliary neurotrophic factor receptor

A structural profile-based computational screen was used to identify neuropoietin (NP), a new cytokine. The np gene is localized in tandem with the cardiotrophin-1 gene on mouse chromosome 7. NP shares structural and functional features with ciliary neurotrophic factor (CNTF), cardiotrophin-1, and cardiotrophin-like cytokine. It acts through a membrane receptor complex comprising CNTF receptor-α component (CNTFRα), gp130, and leukemia inhibitory factor receptor to activate signal transducer and activator of transcription 3 signaling pathway. NP is highly expressed in embryonic neuroepithelia. Strikingly, CNTFRα, but not its alternate ligands, CNTF and cardiotrophin-like cytokine, is expressed at the same developmental stages. NP is also observed in retina and to a lesser extent in skeletal muscle. Moreover, NP could sustain the in vitro survival of embryonic motor neurons and could increase the proliferation of neural precursors when associated to epidermal growth factor and fibroblast growth factor 2. Thus, NP is a new ligand for CNTFRα, with important implications for murine nervous system development

Inactivation of cardiotrophin-like cytokine, a second ligand for ciliary neurotrophic factor receptor, leads to cold-induced sweating syndrome in a patient

Ciliary neurotrophic factor (CNTF) receptor controls a pathway supporting the differentiation and survival of a wide range of neural cell types during development and in adulthood. Cardiotrophin-like cytokine (CLC)–cytokine-like factor 1 (CLF) composite cytokine is a second ligand for the CNTF α-component receptor (CNTFRα). This composite cytokine is built on the structural model of IL-12, with a complex formed by a four-helix bundle type I cytokine, CLC (also referred to as CLCF1), bound to a soluble receptor subunit, CLF (also known as CRLF1). We have reported mutations in the chaperone soluble receptor CLF, causing cold-induced sweating syndrome (CISS). In this study, we studied the CLC-mutated alleles in a patient suffering from a similar disease. This patient was compound heterozygous for two different CLC mutations. The first allele was inactivated by a stop codon at position 107 (Y107X). In the second allele, a R197L mutation in the CLC-predicted binding site to the CNTFRα was detected. Functional analysis of the mutated protein revealed an incapacity for R197L CLC to bind to CNTFRα and activate the subsequent signaling events. Structural and docking interaction studies showed that the R197L substitution destabilized the contact site between CLC and CNTFRα