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StarD7 is a phosphatidylcholine (PC)-specific lipid transfer protein essential for the maintenance of mitochondrial PC composition, morphogenesis, and respiration. Here, we studied the role of StarD7 in skeletal myoblast differentiation using mouse myoblast C2C12 cells and human primary myoblasts. Immunofluorescence and immuno-electron microscopy revealed that StarD7 was distributed in the cytosol, inner mitochondria space, and outer leaflet of the outer mitochondrial membrane in C2C12 cells. Unlike human kidney embryonic cell line HEK293 cells, the mitochondrial proteinase PARL was not involved in the processing and maturation of StarD7 in C2C12 cells. StarD7 was constantly expressed during myogenic differentiation of C2C12 cells. The siRNA-mediated knockdown of StarD7 in C2C12 cells and human primary myoblasts significantly impaired myogenic differentiation and reduced the expression of myomaker, myomerger and PGC-1α. The reduction in mitochondrial PC levels and oxygen consumption rates, decreased expression of myomaker, myomerger and PGC-1α, as well as impaired myogenic differentiation, were completely restored when the protein was reintroduced into StarD7-knockout C2C12 cells. These results suggest that StarD7 is important for skeletal myogenesis in mammals. Mitochondrial membranes are composed of two phospholipid bilayers, the inner mitochondrial membrane (IMM) and the outer mitochondrial membrane (OMM). These mitochondrial membranes are essential for compartmentalization of the organelle and for various mitochondrial functions. More than half of the phospholipids in mitochondrial membranes are phosphatidylcholine (PC), followed by phosphatidylethanolamine (PE) (30-40%), cardiolipin (CL) (5-15%), phosphatidylinositol (PI) (2-9%), phosphatidylserine (PS) (1%) and phosphatidylglycerol (PG) (<1%). Mitochondria have enzymes for the biosynthesis of PE, CL and PG but lack the enzymes required for PC, PI and PS synthesis. These lipids are therefore likely supplied from organelles including as the endoplasmic reticulum (ER) which contain the biosynthesis systems for these phospholipids 1,2. Several previous studies have proposed that phospholipids are transferred between the ER and mitochondria via ER-mitochondria contact sites. In yeast, the formation of contact sites is mediated by a protein complex, the ER-mitochondria encounter structure (ERMES) 3. ERMES comprises four core subunits: Mmm1, Mdm10, Mdm34 and Mdm12. Recent studies demonstrated that the Mmm1-Mdm12 complex directly facilitates PS/PE transfer between the ER and mitochondria in vitro and in vivo 4-6. In mammals, ER-mitochondria contact sites are referred to as ER mitochondria-associated membranes (MAM). Several proteins such as mitofusin 2 (MFN2) 7,8 , glucose-regulated protein 75 (GRP75) 9 , mitochondrial fission 1 protein (Fis1) and B-cell receptor-associated protein 31 (Bap31) 10 have been reported to be implicated in the formation of membrane contact sites. A recent study

Epithelial sodium channel (ENaC) is a Na þ -selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na þ absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCa, b and g subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCa, b and g proteins. The nENaCa, b and g subunits are closely related to amphibian ENaCa, b and g subunits, respectively. Three ENaC subunit mRNAs were highly expressed in the gills, kidney and rectum. Amiloride-sensitive sodium current was recorded from Xenopus oocytes injected with the nENaCabg subunit complementary RNAs under a two-electrode voltage clamp. nENaCa immunoreactivity was observed in the apical cell membrane of the gills, kidney and rectum. Thus, nENaC may play a role in regulating sodium transport of the lungfish, which has a renin -angiotensin-aldosterone system. This is interesting because there may have been an ENaC sodium absorption system controlled by aldosterone before the conquest of land by vertebrates.

We recently reported a female-biased sexually dimorphic area in the mouse brain in the boundary region between the preoptic area and the bed nucleus of the stria terminalis (BNST). We reexamined this area and found that it is a ventral part of the principal nucleus of the BNST (BNSTp). The BNSTp is a male-biased sexually dimorphic nucleus, but the ventral part of the BNSTp (BNSTpv) exhibits female-biased sex differences in volume and neuron number. The volume and neuron number of the BNSTpv were increased in males by neonatal orchiectomy and decreased in females by treatment with testosterone, dihydrotestosterone, or estradiol within 5 days after birth. Sex differences in the volume and neuron number of the BNSTpv emerged before puberty. These sex differences became prominent in adulthood with increasing volume in females and loss of neurons in males during the pubertal/adolescent period. Prepubertal orchiectomy did not affect the BNSTpv, although prepubertal ovariectomy reduced the volume increase and induced loss of neurons in the female BNSTpv. In contrast, the volume and neuron number of male-biased sexually dimorphic nuclei that are composed of mainly calbindin neurons and are located in the preoptic area and BNST were decreased by prepubertal orchiectomy but not affected by prepubertal ovariectomy. Testicular testosterone during the postnatal period may defeminize the BNSTpv via binding directly to the androgen receptor and indirectly to the estrogen receptor after aromatization, although defeminization may proceed independently of testicular hormones in the pubertal/adolescent period. Ovarian hormones may act to feminize the BNSTpv during the pubertal/adolescent period.