Mice lacking desmocollin 1 show epidermal fragility accompanied by barrier defects and abnormal differentiation.

The desmosomal cadherin desmocollin (Dsc)1 is expressed in upper epidermis where strong adhesion is required. To investigate its role in vivo, we have genetically engineered mice with a targeted disruption in the Dsc1 gene. Soon after birth, null mice exhibit flaky skin and a striking punctate epidermal barrier defect. The epidermis is fragile, and acantholysis in the granular layer generates localized lesions, compromising skin barrier function. Neutrophils accumulate in the lesions and further degrade the tissue, causing sloughing (flaking) of lesional epidermis, but rapid wound healing prevents the formation of overt lesions. Null epidermis is hyperproliferative and overexpresses keratins 6 and 16, indicating abnormal differentiation. From 6 wk, null mice develop ulcerating lesions resembling chronic dermatitis. We speculate that ulceration occurs after acantholysis in the fragile epidermis because environmental insults are more stringent and wound healing is less rapid than in neonatal mice. This dermatitis is accompanied by localized hair loss associated with formation of utriculi and dermal cysts, denoting hair follicle degeneration. Possible resemblance of the lesions to human blistering diseases is discussed. These results show that Dsc1 is required for strong adhesion and barrier maintenance in epidermis and contributes to epidermal differentiation.     

AMINO ACID TRANSPORT IN NITZSCHIA OVALIS ARNOTT1,2

The marine diatom Nitzschia ovalis possesses at, least 3 amino acid uptake systems, specific for transport of acidic, polybasic, and, neutral amino acids. Maximum uptake velocity (V_max) for each, site is inversely related to the nitrogen content of the cell, and to the nitrogen available in the culture medium. Transport, of polybasic amino acids occurs throughout the course of growth in batch, culture, but the V_max increases dramatically as the culture ages and nitrogen/cell reaches a low value. K_s does not, change significantly. Acidic and neutral amino acids are taken up only by cells harvested from nitrogen-poor culture. It appears that amino acid transport is repressed by high concentrations of nitrogen in the medium. Under natural conditions, where nitrogen concentrations are low, the contribution of amino acid uptake to the nitrogen economy of Nitzschia populations may be significant.     

Advances in the molecular genetics of obesity.

The past year has seen substantial progress in our understanding the molecular mechanisms of bodyweight regulation, particularly in the central and peripheral actions of the leptin and melanocortin signaling pathways (e.g. leptin stimulation of angiogenesis and suppression of cytokine production). Important advances also include the identification of mutations in components of the leptin and melanocortin pathways in human obese families. Expanding from the positional cloning of leptin some five years ago, the mouse continues to be a central focus of study, particularly the way in which different bodyweight-sensing pathways interact in different feeding states.     

Nesting behavior of the icefish Chaenocephalus aceratus at Bouvetøya Island, Southern Ocean

We describe in situ observations on nesting by the Scotia Sea (or blackfin) icefish Chaenocephalus aceratus (Lönnberg) that constitute the first substantive evidence of egg brooding and parental care by species of the family Channichthyidae. At Boutetoya Island six fish, all apparently male, were observed guarding egg nests at depths of 141–148 m during an ROV deployment. Eggs were laid as aggregated, round masses (~20–25 cm diameter) in shallow, circular depressions (~1-m diameter, ~20-cm depth) that were probably excavated by the parent(s) to protect the nests. The fish guardians remained tenaciously in contact with the eggs despite disturbances caused by the ROV, reacting to this threat with stress and defense behaviors. Because brooding fishes are more susceptible to the population impacts from trawl fisheries, we argue that this life history should be kept in mind in designing management schemes.     

An altered pattern of circulating apolipoprotein E3 isoforms is implicated in preeclampsia

Preeclampsia is a common pregnancy complication that is an important cause of preterm birth and fetal growth restriction. Because there is no diagnostic test yet available for preeclampsia, we used a proteomic approach to identify novel serum/plasma biomarkers for this condition. We conducted case control studies comparing nulliparous women who developed preeclampsia at 36-38 weeks of gestation with healthy nulliparous women matched by gestational age at sampling. Serum/plasma was depleted of six abundant proteins and analyzed by two-dimensional gel electrophoresis (n = 12 per group) and difference gel electrophoresis (n = 12 per group). Differences in abundance of protein spots were detected by univariate and multivariate statistical analyses. Proteins were identified by mass spectrometry and expression of selected proteins was validated by immunoblotting. Proteins whose concentrations were selectively associated with preeclampsia included apolipoprotein E (apoE), apoC-II, complement factor C3c, fibrinogen, transthyretin, and complement factor H-related protein 2. An increase in a deglycosylated isoform of apoE3 and concomitantly decreased amounts of one apoE3 glycoisoform were identified in preeclamptic plasma and confirmed by immunoblotting. Altered production of these preeclampsia-related apoE3 isoforms might impair reverse cholesterol transport, contributing to arterial damage. These findings point to a novel mechanistic link between preeclampsia and subsequent cardiovascular disease.     

Characterization of a membrane protein folding motif, the Ser zipper, using designed peptides

Polar residues play important roles in the association of transmembrane helices and the stabilities of membrane proteins. Although a single Ser residue in a transmembrane helix is unable to mediate a strong association of the helices, the cooperative interactions of two or more appropriately placed serine hydroxyl groups per helix has been hypothesized to allow formation of a "serine zipper" that can stabilize transmembrane helix association. In particular, a heptad repeat Sera Xxx Xxx Leud Xxx Xxx Xxx (Xxx is a hydrophobic amino acid) appears in both antiparallel helical pairs of polytopic membrane proteins as well as the parallel helical dimerization motif found in the murine erythropoietin receptor. To examine the intrinsic conformational preferences of this motif independent of its context within a larger protein, we synthesized a peptide containing three copies of a SeraLeud heptad motif. Computational results are consistent with the designed peptide adopting either a parallel or antiparallel structure, and conformational search calculations yield the parallel dimer as the lowest energy configuration, which is also significantly more stable than the parallel trimer. Analytical ultracentrifugation indicated that the peptide exists in a monomer-dimer equilibrium in dodecylphosphocholine micelles. Thiol disulfide interchange studies showed a preference for forming parallel dimers in micelles. In phospholipid vesicles, only the parallel dimer was formed. The stability of the SerZip peptide was studied in vesicles prepared from phosphatidylcholine (PC) lipids of different chain length: POPC (C16:0C18:1 PC) and DLPC (C12:0PC). The stability was greater in POPC, which has a good match between the length of the hydrophobic region of the peptide and the bilayer length. Finally, mutation to Ala of the Ser residues in the SerZip motif gave rise to a relatively small decrease in the stability of the dimer, indicating that packing interactions rather than hydrogen-bonding provided the primary driving force for association.