Skeletal dysplasias are group of rare genetic diseases resulting from mutations in genes encoding structural proteins of the cartilage extracellular matrix (ECM), signaling molecules, transcription factors, epigenetic modifiers, and several intracellular proteins. Cell division, organelle maintenance, and intracellular transport are all orchestrated by the cytoskeleton-associated proteins, and intracellular processes affected through microtubule-associated movement are important for the function of skeletal cells. Among microtubule-associated motor proteins, kinesins in particular have been shown to play a key role in cell cycle dynamics, including chromosome segregation, mitotic spindle formation, and ciliogenesis, in addition to cargo trafficking, receptor recycling, and endocytosis. Recent studies highlight the fundamental role of kinesins in embryonic development and morphogenesis and have shown that mutations in kinesin genes lead to several skeletal dysplasias. However, many questions concerning the specific functions of kinesins and their adaptor molecules as well as specific molecular mechanisms in which the kinesin proteins are involved during skeletal development remain unanswered. Here we present a review of the skeletal dysplasias resulting from defects in kinesins and discuss the involvement of kinesin proteins in the molecular mechanisms that are active during skeletal development.

The maize abnormal chromosome 10 (Ab10) haplotype encodes a meiotic drive system that converts heterochromatic knobs into centromere-like bodies that are preferentially segregated through female meiosis. Ab10 was first described in the 1940s and has been intensively studied. Here I provide a comprehensive review of the literature, starting from the discovery of knobs and Ab10, preceding through the classic literature, and finishing with molecular structure and mechanisms. The defining features of the Ab10 haplotype are its two specialized kinesins, Kinesin driver and TR-1 kinesin, that activate neocentromeres at knobs containing different classes of the tandem repeat. In most Ab10 haplotypes, the two kinesin/knob systems cooperate to promote maximum meiotic drive. However, recent interpretations suggest that each kinesin/knob system can function as an independent meiotic driver and that in some cases they compete with each other. Ab10 is present at low frequencies throughout the genus Zea and has significantly expanded genome size by promoting the formation of knobs throughout the genome.

Kinesins are P-loop NTPases that can do mechanical work. Like small G-proteins, to which they are related, kinesins execute a program of active site conformational changes that cleaves the terminal phosphate from an NTP substrate. But unlike small G-proteins, kinesins can amplify and harness these conformational changes in order to exert force. In this short review I summarize current ideas about how the kinesin active site works and outline how the active site chemistry is coupled to the larger-scale structural cycle of the kinesin motor domain. Focusing largely on kinesin-1, the best-studied kinesin, I discuss how the active site switch machinery of kinesin cycles between three distinct states, how docking of the neck linker stabilizes two of these states, and how tension-sensitive and position-sensitive neck linker docking may modulate both the hydrolysis step of ATP turnover and the trapping of product ADP in the active site. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 476-482, 2016.