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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2007.07.022 Byline: Kerry Ann Miller (a), John Barrow (a), J. Martin Collinson (a), Scott Davidson (a), Marissa Lear (a), Robert E. Hill (b), Alasdair MacKenzie (a) Keywords: Transcriptional regulation; Comparative genomics; Transgenic mouse; Limb bud muscle precursor cells; Msx1; Pax3; Tcf4; Wnt signalling Abstract: The product of the Msx1 gene is a potent inhibitor of muscle differentiation. Msx1 is expressed in muscle precursor cells of the limb bud that also express Pax3. It is thought that Msx1 may facilitate distal migration by delaying myogenesis in these cells. Despite the role played by Msx1 in inhibiting muscle differentiation, nothing is known of the mechanisms that support the expression of the Msx1 gene within limb bud muscle precursor cells. In the present study we have used a combination of comparative genomics, mouse transgenic analysis, in situ hybridisation and immunohistochemistry to identify a highly conserved and tissue-specific regulatory sub-domain within the previously characterised Msx1 gene proximal enhancer element that supports the expression of the Msx1 gene in Pax3-expressing mouse limb pre-muscle masses. Furthermore, using a combination of in situ hybridisation, in vivo ChIP assay and transgenic explant culture analysis we provide evidence that Msx1 expression in limb bud muscle precursor cells is dependent on the canonical Wnt/TCF signalling pathway that is important in muscle shape formation. The results of these studies provide evidence of a mechanistic link between the Wnt/TCF and the Msx1/Pax3/MyoD pathways within limb bud muscle precursor cells. Author Affiliation: (a) School of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK (b) MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK Article History: Received 9 February 2007; Revised 18 July 2007; Accepted 21 July 2007

The roles of Pax6 were investigated in the murine eye and the olfactory epithelium by analysing gene expression and distribution of [Pax6.sup.-/-] cells in [Pax6.sup.+/+] [left and right arrow] [Pax6.sup.-/-] chimeras. It was found that between embryonic days E10.5 and E16.5 Pax6 is autonomously required for cells to contribute fully not only to the corneal epithelium, where Pax6 is expressed at high levels, but also to the to the corneal stroma and endothelium, where the protein is detected at very low levels, [Pax6.sup.-/-] cells contributed only poorly to the neural retina, forming small clumps of cells that were normally restricted to the ganglion cell layer at E16.5. [Pax6.sup.-/-] cells in the retinal pigment epithelium could express Trp2, a component of the pigmentation pathway, at E14.5 and a small number went on to differentiate and produce pigment at E16.5. The segregation and near-exclusion of mutant cells from the nasal epithelium mirrored the behaviour of mutant cells in other developmental contexts, particularly the lens, suggesting that common primary defects may be responsible for diverse Pax6-related phenotypes. Keywords: Chimera; Chimaera; Pax6; Eye development; Olfactory epithelium; Cornea; Retina; Lens

Mutations in the Pax6 gene disrupt telencephalic development, resulting in a thin cortical plate, expansion of proliferative layers, and the absence of the olfactory bulb. The primary defect in the neuronal cell population of the developing cerebral cortex was analysed by using mouse chimeras containing a mixture of wild-type and Pax6-deficient cells. The chimeric analysis shows that Pax6 influences cellular activity throughout corticogenesis. At early stages, Pax6-deficient and wildtype cells segregate into exclusive patches, indicating an inability of different cell genotypes to interact. At later stages, cells are sorted further based on telencephalic domains. Pax6-deficient cells are specifically reduced in the mediocaudal domain of the dorsal telencephalon, indicating a role in regionalization. In addition, Pax6 regulates the process of radial migration of neuronal precursors. Loss of Pax6 particularly affects movement of neuronal precursors at the subventricular zone/intermediate zone boundary at a transitional migratory phase essential for entry into the intermediate zone. We suggest that the primary role of Pax6 is the continual regulation of cell surface properties responsible for both cellular identity and radial migration, defects of which cause regional cell sorting and abnormalities of migration in chimeras. Keywords: Pax6; Small eye; Cerebral cortex; Neuronal migration; Cell autonomous

Abstract Background Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development. We have studied eye development in a species of true mole, the Iberian mole Talpa occidentalis, and present the molecular basis of abnormal lens development. This is the first embryological developmental study of the eyes of any fossorial mammal at the molecular level. Results Lens fibre differentiation is not completed in the Iberian mole. Although eye development starts normally (similar to other model species), defects are seen after closure of the lens vesicle. PAX6 is not down-regulated in developing lens fibre nuclei, as it is in other species, and there is ectopic expression of FOXE3, a putative downstream effector of PAX6, in some, but not all lens fibres. FOXE3-positive lens fibres continue to proliferate within the posterior compartment of the embryonic lens, but unlike in the mouse, no proliferation was detected anywhere in the postnatal mole lens. The undifferentiated status of the anterior epithelial cells was compromised, and most of them undergo apoptosis. Furthermore, β-crystallin and PROX1 expression patterns are abnormal and our data suggest that genes encoding β-crystallins are not directly regulated by PAX6, c-MAF and PROX1 in the Iberian mole, as they are in other model vertebrates. Conclusion In other model vertebrates, genetic pathways controlling lens development robustly compartmentalise the lens into a simple, undifferentiated, proliferative anterior epithelium, and quiescent, anuclear, terminally differentiated posterior lens fibres. These pathways are not as robust in the mole, and lead to loss of the anterior epithelial phenotype and only partial differentiation of the lens fibres, which continue to express 'epithelial' genes. Paradigms of genetic regulatory networks developed in other vertebrates appear not to hold true for the Iberian mole.

Abstract Background The apparent rediscovery of the Ivory-billed Woodpecker Campephilus principalis in Arkansas, USA, previously feared extinct, was supported by video evidence of a single bird in flight (Fitzpatrick et al, Science 2005, 308:1460–1462). Plumage patterns and wingbeat frequency of the putative Ivory-billed Woodpecker were said to be incompatible with the only possible confusion species native to the area, the Pileated Woodpecker Dryocopus pileatus. Results New video analysis of Pileated Woodpeckers in escape flights comparable to that of the putative Ivory-billed Woodpecker filmed in Arkansas shows that Pileated Woodpeckers can display a wingbeat frequency equivalent to that of the Arkansas bird during escape flight. The critical frames from the Arkansas video that were used to identify the bird as an Ivory-billed Woodpecker are shown to be equally, or more, compatible with the Pileated Woodpecker. Conclusion The identification of the bird filmed in Arkansas in April 2004 as an Ivory-billed Woodpecker is best regarded as unsafe. The similarities between the Arkansas bird and known Pileated Woodpeckers suggest that it was most likely a Pileated Woodpecker.

Abstract Background Congenital aniridia caused by heterozygousity at the PAX6 locus is associated with ocular surface disease including keratopathy. It is not clear whether the keratopathy is a direct result of reduced PAX6 gene dosage in the cornea itself, or due to recurrent corneal trauma secondary to defects such as dry eye caused by loss of PAX6 in other tissues. We investigated the hypothesis that reducing Pax6 gene dosage leads to corneal wound-healing defects. and assayed the immediate molecular responses to wounding in wild-type and mutant corneal epithelial cells. Results Pax6+/- mouse corneal epithelia exhibited a 2-hour delay in their response to wounding, but subsequently the cells migrated normally to repair the wound. Both Pax6+/+ and Pax6+/- epithelia activated immediate wound-induced waves of intracellular calcium signaling. However, the intensity and speed of propagation of the calcium wave, mediated by release from intracellular stores, was reduced in Pax6+/- cells. Initiation and propagation of the calcium wave could be largely decoupled, and both phases of the calcium wave responses were required for wound healing. Wounded cells phosphorylated the extracellular signal-related kinases 1/2 (phospho-ERK1/2). ERK1/2 activation was shown to be required for rapid initiation of wound healing, but had only a minor effect on the rate of cell migration in a healing epithelial sheet. Addition of exogenous epidermal growth factor (EGF) to wounded Pax6+/- cells restored the calcium wave, increased ERK1/2 activation and restored the immediate healing response to wild-type levels. Conclusion The study links Pax6 deficiency to a previously overlooked wound-healing delay. It demonstrates that defective calcium signaling in Pax6+/- cells underlies this delay, and shows that it can be pharmacologically corrected. ERK1/2 phosphorylation is required for the rapid initiation of wound healing. A model is presented whereby minor abrasions, which are quickly healed in normal corneas, transiently persist in aniridic patients, compromising the corneal stroma.

Mitochondrial genes were sequenced from four specimens of the extinct Canary Islands Oystercatcher Haematopus meadewaldoi and compared with African Oystercatcher Haematopus moquini, Eurasian Oystercatcher Haematopus ostralegus and an old unidentified extralimital 'black' oystercatcher specimen from The Gambia. At these loci, H. meadewaldoi was approximately 99.65% identical to multiple Eurasian Oystercatcher samples and in phylogenetic trees fell within the range of genetic variation observed in that species. The mystery Gambian bird was resolved as an extralimital H. moquini. We conclude that H. meadewaldoi was most likely a recently diverged melanistic morph or subspecies of H. ostralegus, although further genomic studies will be required to determine whether there has been a period of isolation followed by introgression. [ABSTRACT FROM AUTHOR]

Recent taxonomic changes to 'Eastern Stonechats' have separated Stejneger's Stonechat Saxicola stejnegeri from the five taxa that now comprise Siberian Stonechat S. maurus. This brings previously unexplored identification and recording challenges. This paper summarises the current knowledge of stonechat taxonomy, and the identification and British status of the 'Eastern Stonechat' taxa that are known to have occurred here, with particular reference to the appearance of genetically sampled individuals in Britain and Europe. It also sets out BBRC's approach to identifying and recording 'Eastern Stonechats'. [ABSTRACT FROM AUTHOR]

The role of the core planar cell polarity (PCP) pathway protein, Vangl2, was investigated in the corneal epithelium of the mammalian eye, a paradigm anatomical model of planar cell migration. The gene was conditionally knocked out in vivo and knocked down by siRNA, followed by immunohistochemical, behavioural and morphological analysis of corneal epithelial cells. The primary defects observed in vivo were of apical‐basal organisation of the corneal epithelium, with abnormal stratification throughout life, mislocalisation of the cell membrane protein, Scribble, to the basal side of cells, and partial loss of the epithelial basement membrane. Planar defects in migration after wounding and in the presence of an applied electric field were noted. However, knockdown of Vangl2 also retarded cell migration in individual cells that had no contact with their neighbours, which precluded a classic PCP mechanism. It is concluded that some of the planar polarity phenotypes in PCP mutants may arise from disruption of apical‐basal polarity. [ABSTRACT FROM AUTHOR]

Abstract A Pale-legged Leaf Warbler Phylloscopus tenellipes was discovered dead after hitting a window at the lighthouse on St Agnes, Isles of Scilly, on 21st October 2016. Feathers taken from the bird were sent for DNA analysis, which confirmed the bird to be a Pale-legged Leaf Warbler and eliminated the morphologically similar Sakhalin Leaf Warbler P. borealoides. An earlier record of one of this species pair from Portland, Dorset, on 22nd October 2012 concerned a bird photographed and seen well by several observers, but it was not possible to establish which species was involved. Full details of both sightings are described here. This is the first record of Pale-legged Leaf Warbler for Britain and the Western Palearctic, and the species has been added to Category A of the British List. [ABSTRACT FROM AUTHOR]

Three subspecies o f C om m on C hiffchaff Phylloscopus co llybita have occurred in B ritain.‘Siberian Chiffchaff' P. c. tristis is now recognised as a scarce but regular m igrant to w e stern Europe, b u t the e x tra lim ita l status o f presum ed Scandinavian individuals o f P. c. abietinus is uncertain. Identification issues and the problem o f abietinus x tristis intergrades remain.This paper summarises the results o f genetic analyses o f 149 migrant and w intering Chiffchaffs in Britain & Ireland during 2009-17. G enetically confirm ed Siberian Chiffchaffs w ere found to be prim arily late-autumn migrants, w ith a num ber of overw intering birds and a small peak o f early spring migrants. M ost Siberian Chiffchaffs in Britain & Ireland are males. In our sample, abietinus was much less frequent than tristis; this subspecies is probably overlooked, w ith records in late autumn, w in te r and a few in the late spring. [ABSTRACT FROM AUTHOR]

A notable gathering of w in te rin g C om m on Chiffchaffs Phylloscopus olly b ita at Nigg Bay, N orth-east Scotland, form s the basis o f this short paper. In addition to field observations, six o f the seven birds w ere trapped and ringed, w hich facilitated sound recordings and/or genetic analysis o f these individuals. A close examination of plumage characters suggested that six o f the seven were m ost like ‘Siberian Chiffchaff' P. c. tris tis , but w ith m inor deviations from ‘classic' tris tis . Data from sound recordings and D N A suggest that all six are best treated as tris tis . The wider implications for subspecies identification of Chiffchaffs in Britain are discussed. [ABSTRACT FROM AUTHOR]