Mutations in the gene encoding lecithin retinol acyltransferase are associated with early-onset severe retinal dystrophy

The chromophore of the visual pigments, 11-cis retinal, is derived from vitamin A (all-trans retinol) through a series of reactions that take place in retinal pigment epithelium (RPE); (ref. 1). The first of these reactions is catalyzed by lecithin retinol acyltransferase (LRAT); (ref. 2). We screened 267 retinal dystrophy patients for mutations in LRAT and identified disease-associated mutations (S175R and 396delAA) in three individuals with severe, early-onset disease. We showed that the S175R mutant has no acyltransferase activity in transfected COS-7 cells. Our findings highlight the importance of genetic defects in vitamin A metabolism as causes of retinal dystrophies and extend prospects for retinoid replacement therapy in this group of diseases.     

Mammalian SWI/SNF complexes promote MyoD-mediated muscle differentiation

Mammalian SWI/SNF complexes are ATP-dependent chromatin remodeling enzymes that have been implicated in the regulation of gene expression, cell-cycle control and oncogenesis. MyoD is a muscle-specific regulator able to induce myogenesis in numerous cell types. To ascertain the requirement for chromatin remodeling enzymes in cellular differentiation processes, we examined MyoD-mediated induction of muscle differentiation in fibroblasts expressing dominant-negative versions of the human brahma-related gene-1 (BRG1) or human brahma (BRM), the ATPase subunits of two distinct SWI/SNF enzymes. We find that induction of the myogenic phenotype is completely abrogated in the presence of the mutant enzymes. We further demonstrate that failure to induce muscle-specific gene expression correlates with inhibition of chromatin remodeling in the promoter region of an endogenous muscle-specific gene. Our results demonstrate that SWI/SNF enzymes promote MyoD-mediated muscle differentiation and indicate that these enzymes function by altering chromatin structure in promoter regions of endogenous, differentiation-specific loci.     

Hybridization between a rare and introduced Oenothera along the north Pacific Coast

Interspecific hybridization has increasingly become regarded as a serious threat to the genetic integrity and persistence of rare plants. Oenothera glazioviana (Onagraceae) is a horticultural species that has escaped cultivation and now threatens the narrow Pacific coastal endemic O. wolfii with hybridization. Reports of morphologically intermediate and ecologically aggressive forms prompted this investigation into the extent of hybridization over the range of O. wolfii . In particular, this study identifies populations of pure and hybrid origins. We used multivariate methods to characterize the morphological variation of Oregon and northern California coastal Oenothera populations. Putatively pure O. wolfii and O. glazioviana individuals do not overlap in many floral characteristics. We found morphologies ranging between the 2 species in northern California populations, however, supporting the inference of hybridization. Remote O. wolfii populations in Oregon were smaller in almost all characters, and discriminant analysis was able to distinguish the rare species from both hybrids and O. glazioviana . However, 5 of 10 O. wolfii populations overlapped significantly with hybrid populations for individual traits and composite morphology, and trait values outside the range of O. wolfii were discovered in 2 populations previously considered to be pure. We also discuss the morphological evidence in light of these species’ chromosomal complexes and environmental factors.     

Chronological evidence that the Moon is either young or did not have a global magma ocean

Chemical evolution of planetary bodies, ranging from asteroids to the large rocky planets, is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth. The Earth's Moon is the archetypical example of this type of differentiation. Evidence for a lunar magma ocean is derived largely from the widespread distribution, compositional and mineralogical characteristics, and ancient ages inferred for the ferroan anorthosite (FAN) suite of lunar crustal rocks. The FANs are considered to be primary lunar flotation-cumulate crust that crystallized in the latter stages of magma ocean solidification. According to this theory, FANs represent the oldest lunar crustal rock type. Attempts to date this rock suite have yielded ambiguous results, however, because individual isochron measurements are typically incompatible with the geochemical make-up of the samples, and have not been confirmed by additional isotopic systems. By making improvements to the standard isotopic techniques, we report here the age of crystallization of FAN 60025 using the (207)Pb-(206)Pb, (147)Sm-(143)Nd and (146)Sm-(142)Nd isotopic systems to be 4,360?±?3 million years. This extraordinarily young age requires that either the Moon solidified significantly later than most previous estimates or the long-held assumption that FANs are flotation cumulates of a primordial magma ocean is incorrect. If the latter is correct, then much of the lunar crust may have been produced by non-magma-ocean processes, such as serial magmatism.     

An ancient recipe for flood-basalt genesis

Large outpourings of basaltic lava have punctuated geological time, but the mechanisms responsible for the generation of such extraordinary volumes of melt are not well known. Recent geochemical evidence suggests that an early-formed reservoir may have survived in the Earth's mantle for about 4.5 billion years (ref. 2), and melts of this reservoir contributed to the flood basalt emplaced on Baffin Island about 60 million years ago. However, the volume of this ancient mantle domain and whether it has contributed to other flood basalts is not known. Here we show that basalts from the largest volcanic event in geologic history--the Ontong Java plateau--also exhibit the isotopic and trace element signatures proposed for the early-Earth reservoir. Together with the Ontong Java plateau, we suggest that six of the largest volcanic events that erupted in the past 250 million years derive from the oldest terrestrial mantle reservoir. The association of these large volcanic events with an ancient primitive mantle source suggests that its unique geochemical characteristics--it is both hotter (it has greater abundances of the radioactive heat-producing elements) and more fertile than depleted mantle reservoirs-may strongly affect the generation of flood basalts.     

Astrology

Summary As a divinatory practice, astrology is without equal in both its colorful history and modern day popularity. Astrology has grown, over thousands of years, into a huge and ornate superstructure that lacks a central design. Although astrology has been dimly veiled by its occult mystique for centuries, the light of modern day inquiry has shown its substance to be mostly illusionary and revealed its foundation to be the shakiest possible: that of self-justification and anecdotal evidence. Despite the many claims of its practitioners and followers, extensive investigation has revealed astrology to be a great teetering monument to human gullibility.     

Diolefin analog of a sex pheromone component ofHeliothis zea active in disrupting mating communication

Summary A hydrocarbon (Z)-1, 12-heptadecadiene, was synthesized from the major sex pheromone of the corn earworm,Heliothis zea (Boddie). In field tests, significant disruption of the sexual behavior ofH. zea males was obtained, comparable to the pheromone (Z)-11-hexadecenal. This novel diolefin should be inexpensive, exhibit improved stability, and may lead to improved methods of control.Reprint requests to D.E. Weidhaas, P.O. Box 14565, Gainesville (FL 32604, USA).     

Ontogenic development and anatomical distribution of a supernumerary limb-inducing factor

. .

---

---

This work was supported by a Rackham Grant from the University of Michigan.     

Ultrastructure of photoreceptor cells in a vitamin A-deficient moth (Manduca sexta)

Zusammenfassung Die LepidoptereManduca sexta wurde während mehr als 20 Generationen ohne Vitamin A aufgezogen. Feinstrukturelle Veränderungen traten auf: Die Photorezeptorzellen zeigten starke Zunahme und Desorientierung der Mikrovilli des Rhabdoms. Mitochondrien waren aus der Normallage nahe am Ursprung der Mikrovilli gegen die Peripherie der Retinulazelle verschoben. «Zwiebelkörper» (Sammlungen von konzentrisch angeordneten Mikrovillimembranen) und eine grosse Anzahl von Mikrotubuli wurden in den interretinulären Zellen gefunden. Mit Pflanzendiät aufgezogene Insekten hingegen zeigten keine der beschriebenen Ultrastrukturänderungen.