Male-pattern baldness susceptibility locus at 20p11

We conducted a genome-wide association study for androgenic alopecia in 1,125 men and identified a newly associated locus at chromosome 20p11.22, confirmed in three independent cohorts (n = 1,650; OR = 1.60, P = 1.1 x 10(-14) for rs1160312). The one man in seven who harbors risk alleles at both 20p11.22 and AR (encoding the androgen receptor) has a sevenfold-increased odds of androgenic alopecia (OR = 7.12, P = 3.7 x 10(-15)).     

Maize HapMap2 identifies extant variation from a genome in flux

Whereas breeders have exploited diversity in maize for yield improvements, there has been limited progress in using beneficial alleles in undomesticated varieties. Characterizing standing variation in this complex genome has been challenging, with only a small fraction of it described to date. Using a population genetics scoring model, we identified 55 million SNPs in 103 lines across pre-domestication and domesticated Zea mays varieties, including a representative from the sister genus Tripsacum. We find that structural variations are pervasive in the Z. mays genome and are enriched at loci associated with important traits. By investigating the drivers of genome size variation, we find that the larger Tripsacum genome can be explained by transposable element abundance rather than an allopolyploid origin. In contrast, intraspecies genome size variation seems to be controlled by chromosomal knob content. There is tremendous overlap in key gene content in maize and Tripsacum, suggesting that adaptations from Tripsacum (for example, perennialism and frost and drought tolerance) can likely be integrated into maize.     

Signal requirements in the step-wise functional maturation of cytotoxic T lymphocytes

The generation of effector cytotoxic T lymphocytes from resting precursors proceeds through a series of steps in a pathway that, in aggregate, involves both proliferation and development of cytotoxicity. To understand the relationship of the various signals (mitogens and/or lymphokines) that bring about progress along this pathway, it is desirable to define a series of 'minimal signals', each of which stimulates the cell to proceed to a further stage in this process of differentiation. Stimulation of lymphocytes with two different monoclonal antibodies directed against the CD2 surface molecule induces a proliferative response; we report here that both CD4+ and CD8+ cells proliferate in response to such a stimulus but do not develop cytotoxicity. Addition of recombinant gamma-interferon (rIFN-gamma) or recombinant IL-2 (rIL-2) to the activated cells leads to acquisition of cytotoxic status by the CD8+ cells but not the CD4+ cells. The availability, in addition to precursors and effectors, of an apparently intermediate stage in the form of proliferating CD8+ cells that are non-cytotoxic should facilitate both cellular and molecular studies of this maturation pathway; the differences between CD4+ and CD8+ cells in development of cytotoxicity under these experimental conditions is a valuable model for understanding differentiation of T lymphocytes.     

Common variants at 12q15 and 12q24 are associated with infant head circumference

To identify genetic variants associated with head circumference in infancy, we performed a meta-analysis of seven genome-wide association studies (GWAS) (N = 10,768 individuals of European ancestry enrolled in pregnancy and/or birth cohorts) and followed up three lead signals in six replication studies (combined N = 19,089). rs7980687 on chromosome 12q24 (P = 8.1 × 10(-9)) and rs1042725 on chromosome 12q15 (P = 2.8 × 10(-10)) were robustly associated with head circumference in infancy. Although these loci have previously been associated with adult height, their effects on infant head circumference were largely independent of height (P = 3.8 × 10(-7) for rs7980687 and P = 1.3 × 10(-7) for rs1042725 after adjustment for infant height). A third signal, rs11655470 on chromosome 17q21, showed suggestive evidence of association with head circumference (P = 3.9 × 10(-6)). SNPs correlated to the 17q21 signal have shown genome-wide association with adult intracranial volume, Parkinson's disease and other neurodegenerative diseases, indicating that a common genetic variant in this region might link early brain growth with neurological disease in later life.     

Common variants near MBNL1 and NKX2-5 are associated with infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is a severe condition characterized by hypertrophy of the pyloric sphincter muscle. We conducted a genome-wide association study (GWAS) on 1,001 surgery-confirmed cases and 2,401 controls from Denmark. The six most strongly associated loci were tested in a replication set of 796 cases and 876 controls. Three SNPs reached genome-wide significance. One of these SNPs, rs11712066 (odds ratio (OR) = 1.61; P = 1.5 × 10(-17)) at 3p25.1, is located 150 kb upstream of MBNL1, which encodes a factor that regulates splicing transitions occurring shortly after birth. The second SNP, rs573872 (OR = 1.41; P = 4.3 × 10(-12)), maps to an intergenic region at 3p25.2 approximately 1.3 Mb downstream of MBNL1. The third SNP, rs29784 (OR = 1.42; P = 1.5 × 10(-15)) at 5q35.2, is 64 kb downstream of NKX2-5, which is involved in development of cardiac muscle tissue and embryonic gut development.     

Surprising dissimilarities in a newly formed pair of 'identical twin' stars

The mass and chemical composition of a star are the primary determinants of its basic physical properties-radius, temperature and luminosity-and how those properties evolve with time. Accordingly, two stars born at the same time, from the same natal material and with the same mass, are 'identical twins,' and as such might be expected to possess identical physical attributes. We have discovered in the Orion nebula a pair of stellar twins in a newborn binary star system. Each star in the binary has a mass of 0.41 +/- 0.01 solar masses, identical to within 2 per cent. Here we report that these twin stars have surface temperatures differing by approximately 300 K ( approximately 10 per cent) and luminosities differing by approximately 50 per cent, both at high confidence level. Preliminary results indicate that the stars' radii also differ, by 5-10 per cent. These surprising dissimilarities suggest that one of the twins may have been delayed by several hundred thousand years in its formation relative to its sibling. Such a delay could only have been detected in a very young, definitively equal-mass binary system. Our findings reveal cosmic limits on the age synchronization of young binary stars, often used as tests for the age calibrations of star-formation models.     

A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions

In open star clusters, where all members formed at about the same time, blue straggler stars are typically observed to be brighter and bluer than hydrogen-burning main-sequence stars, and therefore should already have evolved into giant stars and stellar remnants. Correlations between blue straggler frequency and cluster binary star fraction, core mass and radial position suggest that mass transfer or mergers in binary stars dominates the production of blue stragglers in open clusters. Analytic models, detailed observations and sophisticated N-body simulations, however, argue in favour of stellar collisions. Here we report that the blue stragglers in long-period binaries in the old (7?×?10(9)-year) open cluster NGC 188 have companions with masses of about half a solar mass, with a surprisingly narrow mass distribution. This conclusively rules out a collisional origin, as the collision hypothesis predicts a companion mass distribution with significantly higher masses. Mergers in hierarchical triple stars are marginally permitted by the data, but the observations do not favour this hypothesis. The data are highly consistent with a mass transfer origin for the long-period blue straggler binaries in NGC 188, in which the companions would be white dwarfs of about half a solar mass.