morfogene

A morfogene, or morphogen, is a signaling molecule that governs tissue patterning by forming a concentration gradient across a developing tissue and providing cells with positional information that directs their differentiation. The concept is central to how embryos establish axes and organized structures from initially uniform cell populations.

Morphogens are typically produced from localized sources, diffuse through the tissue, and are gradually degraded or sequestered. Cells detect the morphogen concentration through receptors and intracellular signaling pathways, responding only when thresholds are crossed. Different concentration ranges activate distinct gene expression programs, leading to orderly spatial patterns. The gradient's shape and robustness emerge from production rates, diffusion properties, degradation, and interactions with the extracellular matrix and cell movement, as well as feedback mechanisms within signaling networks.

Well-known examples include the Bicoid gradient in the Drosophila embryo, which helps establish anterior-posterior patterning, and Sonic hedgehog (SHH) in vertebrates, which patterns the neural tube and limbs. Other morphogens such as BMPs, Wnts, and Nodal contribute to dorsal-ventral and left-right axis formation and mesoderm specification. The study of morphogens encompasses developmental biology, systems biology, and regenerative medicine, illustrating how concentration-dependent signaling translates into complex tissue architecture.

The morfogene concept was popularized in the late 1960s by Lewis Wolpert, who introduced the French flag model to describe how a single gradient could specify multiple cell fates. Aberrant morphogen signaling can lead to congenital abnormalities and cancer, but controlled manipulation of morphogen gradients holds potential for tissue engineering and regenerative therapies.

See also: morphogenesis, gradient signaling, developmental biology.