Development is determined by genes that interact with cellular and environmental surroundings. Involved gene products include transcription regulators, factors of diffusion of interacting with cells and guides them along specific development pathways to receptors for such factors, structural proteins, intracellular signaling molecules and much more. Not surprisingly, the most numerous developmental disorders encountered in humans, caused by genomic, chromosomal or gene mutations. However, even if the genome is clearly the primary source of information, regulating and defining human development, the role of genes in development is often misinterpreted to be the main. In fact, the genome has no similarities with the plan of the architect, accurately determining what materials should be used and how they should be collected; it is not a literal description of the final form used by all embryonic and fetal structures.
Rather, the genome specifies a set of interacting proteins and non-coding RNAS, indicating the direction of growth, migration, differentiation and apoptosis, in the end, with a high degree of probability leading to the development of normal Mature structures. Thus, for example, there are genetic instructions that indicates that a finger will take the form of hour glass or that the eye is spherical. These forms arise as the intended consequences of development processes, thereby generating a structurally correct cells, tissues and organs.
Shot primary regulators of development, genes, other processes must also play a role. Development is regulated but not determined by the genome, highlights the significant role of probability in normal development. For example, mice have a mutation in the formin gene causes aplasia of kidneys, only 20% of carriers of the mutation, even if the mutation is transmitted inbred animals. I believe that inbred mice are genetically identical at all loci in their genomes, so a 20% penetrance of a single mutation in the formin gene may not be attributed to other modifying genes in mice affected by renal agenesis, compared with unaffected mice. The most plausible explanation for this phenomenon is that the mutation the formin shifts the balance of some evolutionary process, increasing the probability of exceeding the threshold of one of the factors of renal aplasia.
Thus, carriers of the mutation the formin does not always lead to aplasia of the kidneys, and not the rest of the genome, or various non-genetic factors are not responsible for the development of a defect in a small percentage of animals. Probabilistic processes provide a rich source of individual differences that does not always lead to normal development. Thus, the development of is often that “anything can happen”.
Environmental factors and their influence on the development of
The local environment in which the cell or tissue, plays a Central role in ensuring a normal development context. It is not surprising that drugs or other agents coming from the environment, can be teratogens, since they often interfere by binding to molecules involved in the activity of genes. Identification of the mechanism of teratogenesis has a clear sense not only for clinical medicine and public health, but also for basic science; understanding how teratogens cause birth defects, can give an awareness of violations of basic development paths that lead to Vice. As the molecular and cellular pathway used in the course of development, often unique and are not used after maturation, teratogens, causing severe congenital defects, can not have any side effects, in adults, because the mentioned ways are no longer functional or have other goals in adulthood. A typical example is retinoid syndrome fetal observed in women treated during pregnancy medication isotretinoin. Isotretinoin — oral retinoid, designed for systemic treatment of boils.
It causes severe birth defects if used during pregnancy because it mimics the action of endogenous retinoic acid, the substances dispersed in fetal tissues and interact with cells, causing them to follow a specific path of development. Other teratogens often cause a very specific set of birth defects, the risk of which is critically dependent on gestational age at the time of impact, sensitivity of different tissues to teratogen and duration of the impact of teratogens during pregnancy. One of the classic examples thalidomide syndrome. Thalidomide is a sedative drug widely used in the fifties of the XX century, later identified as teratogen.
It causes high incidence of limb deformities in embryos exposed to between the 4th and 8th weeks of gestation, due to the effect on the vascularization of the developing limb. Another example is fetal alcohol syndrome. Alcohol causes a specific set of congenital malformations, including primarily the Central nervous system, because it is relatively more toxic to the developing brain and associated craniofacial structures than for other tissues.
Some teratogens, such as x-ray radiation are also mutagens. The fundamental difference between teratogens and mutagens, the mutagens cause disturbances, creating inheritable changes in the genetic material, whereas teratogens act directly and singly on the developing tissues of the embryo. Thus, the impact on the fetus of mutagen can cause increased risk of birth defects or other diseases (e.g., tumors) throughout a person’s life and even his progeny, and the impact of teratogens increases the risk of birth defects in this, but not in subsequent pregnancies.