Mitochondrial biogenesis is strictly controlled during development and cell differentiation in order to supply the appropriate number of mitochondria structural and functionally differentiated to the various cells of the organism. The process is extremely complex for two main reasons. First, energy requirement varies widely among the different tissues of the organism; second, the biogenesis of the organelle systems located in different subcellular compartments, nucleus and mitochondria. During the last few years considerable effort has been devoted to study the factors that regulate the expression of mitochondrial genes, and, more importantly, the mechanisms involved in nucleo-mitochondrial communication. Some transcription factors 1 and 2, are essential to orchestrate mitochondrial biogenesis in mammals, and the importance of post transcriptional mechanisms of control, including RNA stability and translational regulation has also been demonstrated. However, many questions remain still unresolved. In particular the mechanisms  that regulate mitochondrial DNA(mtDNA) proliferation or mitochondrial maturation during essential processes such as cell growth and differentiation are practically unknown.

In this review we discuss the evidence obtained in different biological systems supporting the variety of mechanisms involved in mitochondrial biogenesis during development and cell differentiation and the important role that mitochondria play in these processes.