Илүүдэл жин бол хорт хавдарын хоёрдугаарт орох хамгийн чухал эрсдэлт хүчин зүйл

Diverse developmental and degenerative single-gene disorders such as polycystic kidney disease, nephronophthisis, retinitis pigmentosa, the Bardet–Biedl syndrome, the Joubert syndrome, and the Meckel syndrome may be categorized as ciliopathies — a recent concept that describes diseases characterized by dysfunction of a hairlike cellular organelle called the cilium. Most of the proteins that are altered in these single-gene disorders function at the level of the cilium–centrosome complex, which represents nature's universal system for cellular detection and management of external signals. Cilia are microtubule-based structures found on almost all vertebrate cells. They originate from a basal body, a modified centrosome, which is the organelle that forms the spindle poles during mitosis. The important role that the cilium–centrosome complex plays in the normal function of most tissues appears to account for the involvement of multiple organ systems in ciliopathies. In this review, we consider the role of the cilium in disease.

 

Structure and Function of the Cilium–Centrosome Complex

Primary cilia consist of a microtubule-based ciliary axoneme, assembled from a basal body, which represents one of the two centrioles of the centrosome. Primary cilia are surrounded by a membrane lipid bilayer that maintains a lipid and protein content distinct from that of the plasma membrane. Cilia are classified as 9+2 or 9+0, depending on whether the axoneme includes an additional central pair of microtubules.5 The boundary between the ciliary and other cell compartments is demarcated by the transition zone (Figure 1). Motor proteins transport cargo proteins along the ciliary axoneme, a process known as intraflagellar transport.
Cilia are highly conserved throughout evolution. Thus, studies in the green alga Chlamydomonas reinhardtii have identified evolutionarily conserved intraflagellar-transport proteins and have enhanced our understanding of cilia biology.6 Virtually all vertebrate tissues or cell types can produce primary cilia, also termed sensory cilia, which transmit signals to the interior of cells (Figure 1). Cilia sense a wide variety of extracellular signals and transduce them into decisions regarding proliferation, polarity, nerve growth, differentiation, or tissue maintenance. A broad range of signals can be received by specific ciliary receptors, including photosensation, mechanosensation, osmosensation, thermosensation, hormone sensation, and olfactory sensation. Another type of cilia, termed motile cilia, is structurally similar to primary cilia. Genetic defects of motile cilia cause primary ciliary dyskinesia, which characterizes a group of diseases, such as Kartagener's syndrome, that are beyond the scope of this review.