Oceanographic barriers,divergence, and admixture: Phylogeography and taxonomy of two putative subspecies of short‐finned pilot whale

Genomic phylogeography plays an important role in describing evolutionary processes and their geographic, ecological, or cultural drivers. These drivers are often poorly understood in marine environments, which have fewer obvious barriers to mixing than terrestrial environments. Taxonomic uncertainty of some taxa (e.g., cetaceans), due to the difficulty in obtaining morphological data, can hamper our understanding of these processes. One such taxon, the short‐finned pilot whale, is recognized as a single global species but includes at least two distinct morphological forms described from stranding and drive hunting in Japan, the “Naisa” and “Shiho” forms. Using samples (n = 735) collected throughout their global range, we examine phylogeographic patterns of divergence by comparing mitogenomes and nuclear SNP loci. Our results suggest three types within the species: an Atlantic Ocean type, a western/central Pacific and Indian Ocean (Naisa) type, and an eastern Pacific Ocean and northern Japan (Shiho) type. mtDNA control region differentiation indicates these three types form two subspecies, separated by the East Pacific Barrier: Shiho short‐finned pilot whale, in the eastern Pacific Ocean and northern Japan, and Naisa short‐finned pilot whale, throughout the remainder of the species' distribution. Our data further indicate two diverging populations within the Naisa subspecies, in the Atlantic Ocean and western/central Pacific and Indian Oceans, separated by the Benguela Barrier off South Africa. This study reveals a process of divergence and speciation within a globally‐distributed, mobile marine predator, and indicates the importance of the East Pacific Barrier to this evolutionary process.     

Electric-field-induced luminescence emission spectra of Photosystem I and Photosystem II from chloroplasts

The electroluminescence induced by external electric fields in blebs prepared from chloroplasts consists of two kinetically different phases, rapid (R) and slow (S), which were shown to be linked to Photosystem I (PS I) and Photosystem II (PS II) activities, respectively (Symons, M., Korenstein, R. and Malkin, S. (1985) Biochim. Biophys. Acta 806, 305–310). In this report we describe conditions involving heat treatment of broken chloroplasts, which make it possible to observe R phase electroluminescence essentially devoid of any contribution by the S phase. This allowed the precise measurement of the emission spectrum of PS I electroluminescence. The emission spectrum of PS II electroluminescence was obtained using regular broken chloroplasts, which show only S-type emission. The latter emission spectrum is identical to the one obtained for ordinary prompt fluorescence, peaking at 685 nm with a bandwidth of about 25 nm. The PS I emission spectrum is symmetric around 705 nm and is much broader, about 60 nm.     

Selective expression of murine lymphocyte alloantigens controlled by the X-chromosome

Alloantisera specific to X-chromosome linked lymphocyte membrane antigens (Ly-X) were prepared by immunizing F1 male mice with identical F1 female lymphocytes. Independent B cell specific (anti Lyb-X) and T cell specific (anti Lyt-X) antibodies were detected. The Lyt-X antigen was expressed on Lyt-2⁺, 3⁺, and on Tla^–, Lyt-1⁺, 2⁺, 3⁺ T cell subpopulations. The problem of X-chromosome inactivation and the relationship ofH-2-linkedIr genes and Ia antigens, with X-linkedIr genes and lymphocyte alloantigens are discussed.     

Insights in KIR2.1 channel structure and function by an evolutionary approach; cloning and functional characterization of the first reptilian inward rectifier channel KIR2.1, derived from the California kingsnake (Lampropeltis getula californiae)

Potassium inward rectifier K_IR2.1 channels contribute to the stable resting membrane potential in a variety of muscle and neuronal cell-types. Mutations in the K_IR2.1 gene KCNJ2 have been associated with human disease, such as cardiac arrhythmias and periodic paralysis. Crystal structure and homology modelling of K_IR2.1 channels combined with functional current measurements provided valuable insights in mechanisms underlying channel function. K_IR2.1 channels have been cloned and analyzed from all main vertebrate phyla, except reptilians. To address this lacuna, we set out to clone reptilian K_IR2.1 channels. Using a degenerated primer set we cloned the KCNJ2 coding regions from muscle tissue of turtle, snake, bear, quail and bream, and compared their deduced amino acid sequences with those of K_IR2.1 sequences from 26 different animal species obtained from Genbank. Furthermore, expression constructs were prepared for functional electrophysiological studies of ectopically expressed K_IR2.1 ion channels. In general, KCNJ2 gene evolution followed normal phylogenetic patterns, however turtle K_IR2.1 ion channel sequence is more homologues to avians than to snake. Alignment of all 31 K_IR2.1 sequences showed that all disease causing K_IR2.1 mutations, except V93I, V123G and N318S, are fully conserved. Homology models were built to provide structural insights into species specific amino acid substitutions. Snake K_IR2.1 channels became expressed at the plasmamembrane and produced typical barium sensitive (IC₅₀ ∼6 μM) inward rectifier currents.     

Stochastic Dynamics of Interacting Haematopoietic Stem Cell Niche Lineages

Since we still know very little about stem cells in their natural environment, it is useful to explore their dynamics through modelling and simulation, as well as experimentally. Most models of stem cell systems are based on deterministic differential equations that ignore the natural heterogeneity of stem cell populations. This is not appropriate at the level of individual cells and niches, when randomness is more likely to affect dynamics. In this paper, we introduce a fast stochastic method for simulating a metapopulation of stem cell niche lineages, that is, many sub-populations that together form a heterogeneous metapopulation, over time. By selecting the common limiting timestep, our method ensures that the entire metapopulation is simulated synchronously. This is important, as it allows us to introduce interactions between separate niche lineages, which would otherwise be impossible. We expand our method to enable the coupling of many lineages into niche groups, where differentiated cells are pooled within each niche group. Using this method, we explore the dynamics of the haematopoietic system from a demand control system perspective. We find that coupling together niche lineages allows the organism to regulate blood cell numbers as closely as possible to the homeostatic optimum. Furthermore, coupled lineages respond better than uncoupled ones to random perturbations, here the loss of some myeloid cells. This could imply that it is advantageous for an organism to connect together its niche lineages into groups. Our results suggest that a potential fruitful empirical direction will be to understand how stem cell descendants communicate with the niche and how cancer may arise as a result of a failure of such communication.     

Effects of parental and own early developmental conditions on the phenotype in zebra finches (Taeniopygia guttata)

The performance of an individual can be critically influenced by its experience early in life as well as trans-generationally by the conditions experienced by its parents. However, it remains unclear whether or not the early experience of parents and offspring interact with each other and adapt offspring when the parental and own early environmental conditions match. Here, zebra finches (Taeniopygia guttata) that had experienced either early low or high nutritional conditions raised their offspring under either matched or mismatched nutritional conditions. Parental and offspring early conditions both separately affected the offspring’s adult phenotype, but early conditions experienced by parents and offspring did not interact as predicted. Offspring that grew up under conditions matching those their parents had experienced did not do better than those that grew up in a mismatched environment. Thus, transgenerational effects remain a lifelong burden to the offspring acting in addition to the offspring’s own early life experience. The lack of evidence for adaptive programming to matching environmental conditions may result from non-predictive environments under natural conditions in such opportunistic breeders.