Modeling digits. Digit patterning is controlled by a Bmp-Sox9-Wnt Turing network modulated by morphogen gradients

During limb development, digits emerge from the undifferentiated mesenchymal tissue that constitutes the limb bud. It has been proposed that this process is controlled by a self-organizing Turing mechanism, whereby diffusible molecules interact to produce a periodic pattern of digital and interdigital fates. However, the identities of the molecules remain unknown. By combining experiments and modeling, we reveal evidence that a Turing network implemented by Bmp, Sox9, and Wnt drives digit specification. We develop a realistic two-dimensional simulation of digit patterning and show that this network, when modulated by morphogen gradients, recapitulates the expression patterns of Sox9 in the wild type and in perturbation experiments. Our systems biology approach reveals how a combination of growth, morphogen gradients, and a self-organizing Turing network can achieve robust and reproducible pattern formation.

Spectral and sequence similarity between vasoactive intestinal peptide and the second conserved region of human immunodeficiency virus type 1 envelope glycoprotein (gp120): possible consequences on prevention and therapy of AIDS

Recently, in sera of HIV infected individuals, antibodies recognizing nonimmunogenic C-terminal domain of the second conserved region of HIV-1 gp120 were identified (1). These antibodies are significantly more prevalent in asymptomatic carriers than in AIDS patients (1). Here we reported striking spectral and sequence homologies between human vasoactive intestinal peptide (VIP) and the conserved peptide derived from HIV-1 gp120 which binds these antibodies. The possible consequences of these findings on therapy and prevention of AIDS are discussed.