What is "neocentromere"

n. (context genetics English) A functioning centromere in a new location

Neocentromeres are new centromeres that form at a place on the chromosome that is usually not centromeric. They typically arise due to disruption of the normal centromere. These neocentromeres should not be confused with “knobs”, which were also described as “neocentromeres” in maize in the 1950s. Unlike most normal centromeres, neocentromeres do not contain satellite sequences that are highly repetitive but instead consist of unique sequences. Despite this, most neocentromeres are still able to carry out the functions of normal centromeres in regulating chromosome segregation and inheritance. This raises many questions on what is necessary versus what is sufficient for constituting a centromere.

As neocentromeres are still a relatively new phenomenon in cell biology and genetics, it may be useful to keep in mind that neocentromeres may be somewhat related to point centromeres, holocentromeres, and regional centromeres. Whereas point centromeres are defined by sequence, regional and holocentromeres are epigenetically defined by where a specific type of nucleosome (the one containing the centromeric histone H3) is located.

It may also be analytically helpful to take into account that the centromere is generally defined in relation to the kinetochore, specifically as the “part of the chromosome that links two sister chromatids together via the kinetochore”. However, the emergence of research in neocentromeres troubles this conventional definition and questions the function of a centromere beyond being a “landing pad” for kinetochore formation. This expands the scope of the centromere’s function to include regulating the function of the kinetochore and the mitotic spindle.