When it Comes to Limb Development, Marsupials Have a Leg Up

PHOTOMICROGRAPH OF MOUSE BLASTOCYST WITH INNER CELL MASS VISIBLE AT 6 O'CLOCK. EMBRYO MOUSE BLASTOCYST INNER CELL MASS

We have probably all seen these creatures somewhere. After all, the image of a pink undeveloped marsupial embryo living outside its mother’s womb is a staple of nature shows and biology films.  The fact that these mammals do the majority of their developing outside of the womb is enough to set them apart, but new research out of Duke University shows that it is more than just where they develop that is different; their timeline of development is different (1). Continue reading

Worms with the Guts to Play Games of Chance: Stochastic Effects and Binary Output in Gene Expression

How do you explain the phenomenon of incomplete penetrance, which happens when individuals carrying an allele for a given phenotype don’t always express the phenotype? For instance, individuals carrying the same mutation associated with a genetic disease do not always develop that disease.

Sometimes environment influences gene expression and plays a role, or other genetic differences among the individuals of a population can affect the expression of the gene in question. But, incomplete penetrance is also observed in model organisms that are raised in controlled environmental conditions and that have “identical” genetic makeup.

Biologists have proposed that random variability in gene expression could account for such events, and in clonal populations of microorganisms random variation in gene expression may even be important for generating genetic variability. However, in more complex organisms that have specific cell types organized into tissues and organs, gene expression needs to be highly controlled for the organism to develop properly. So, if there are random fluctuations in gene expression, somehow they need to be “buffered” in normal development.

Until the recent Nature paper published by Raj et al. (1), little experimental data existed to support the theory that essential developmental pathways include mechanisms to buffer the effects of random variations in gene expression. Continue reading