Transcription factors guide differences in human and chimp brain function

Kipungi Hybridization Revisited

Recently, two simultaneous studies came to the conclusion that the close relationship of Rungwecebus kipungi to Papio (based on mitochondrial DNA) suggest a hybrid history for the genus/species. Burell et al. 2009 suggest that the kipungi was the result of hybridization between male mangabeys (probably Lophocebus) and female baboons. Zinner et al. 2009, on the other hand, suggest the possibility that the kipungi is a basal member of the Papio clade and fairly recently (until 0.35 million years ago) male kipungis were breeding with female baboons. In this study, Roberts and colleagues include DNA from a separate population of kipungis and find that only one population shows signs of hybridization, suggesting that the originally sampled population did, in fact, hybridize as Zinner and colleagues suggested. However, the newly sampled population shows no signs of hybridization, suggesting that the origins of kipungis were not results of mangabey/baboon hybridization.

A common variation in EDAR is a genetic determinant of shovel-shaped incisors

The association of EDAR 1540C with dental morphology is investigated, and the study indicates that the number of EDAR 1540C alleles is correlated with tooth-shoveling grade. Read all about it!

Global Microsatellite Content Distiguishes Humans, Primates, Animals and Plants

Galindo and colleagues show that global microsatellite content varies predictably by species, with most major differences occurring in developmental regions. Though further study is needed, they suggest that it might be fruitful to look at how global microsatellite content relates to different phenotypes.

Targets of Balancing Selection in the Human Genome

The authors looked at 13400 genes in two human populations for evidence of balancing selection; in particular, they looked for evidence of excess polymorphism and intermediate-frequency alleles. They find 60 candidate genes, and not surprisingly, many factor into immune function, though others encode keratin and membrane channels. Interestingly, they also find possible evidence for population differences in balancing selection between the two groups in 13 of the candidate genes.

Heritability and Demographic Analyses in the Large Isolated Population of Val Borbera Suggest Advantages in Mapping Complex Traits Genes

Genetic studies performed on heterogeneous populations make identifying rare variants for complex diseases difficult because of confounding variables associated with heterogeneous populations. This study collected genetic samples and medical information for 1803 people within a relatively isolated population. The authors report that analysis of the isolated population reveals significant heritability of medically relevant traits that might not have otherwise been uncovered with a more heterogeneous cohort.

Human DNA methylomes at base resolution show widespread epigenomic differences

Human genetic variation extends beyond differences in the underlying genetic sequence. A recent study reported in Nature provides a more robust understanding of DNA cytosine methylation, an alternate source of genetic variation. While DNA methylation was primarily associated with repeat CpG (Cytosine-phosphate-Guanine) rich portions of the genome, Lister et al. report that approximately 25% of methylation in embryonic stem cells occurs in non CpG portions of the genomes. CpG regions are associated with promoter regions of genes, and methylation of these regions are thought to regulate gene expression. The report of methylation in non CpG regions raises new questions about the role of this epigenetic modification. The publication also represents one of the first papers describing a relatively complete map of the human epigenome.