Genetics of X Inactivation

By Michael Bodega - I (Michael Bodega) created this work entirely by myself., Public Domain, https://commons.wikimedia.org/w/index.php?curid=16831523

X inactivation shuts off many (but not all!) genes of one of the X chromosomes in the cells of female mammals, to balance gene expression with cells of males that have only one X chromosome.  The inactivation tends to be random (as to which of the pair of X chromosomes experiences inactivation in each cell), and has phenotypic consequences for health and disease  and also affects fur color in female cats.  The set of inactivated X chromosome genes in female human cells has been analyzed, which may help in understanding X-linked disorders in females.  Abstract:

X chromosome inactivation (XCI) silences transcription from one of the two X chromosomes in female mammalian cells to balance expression dosage between XX females and XY males. XCI is, however, incomplete in humans: up to one-third of X-chromosomal genes are expressed from both the active and inactive X chromosomes (Xa and Xi, respectively) in female cells, with the degree of 'escape' from inactivation varying between genes and individuals. The extent to which XCI is shared between cells and tissues remains poorly characterized, as does the degree to which incomplete XCI manifests as detectable sex differences in gene expression and phenotypic traits. Here we describe a systematic survey of XCI, integrating over 5,500 transcriptomes from 449 individuals spanning 29 tissues from GTEx (v6p release) and 940 single-cell transcriptomes, combined with genomic sequence data. We show that XCI at 683 X-chromosomal genes is generally uniform across human tissues, but identify examples of heterogeneity between tissues, individuals and cells. We show that incomplete XCI affects at least 23% of X-chromosomal genes, identify seven genes that escape XCI with support from multiple lines of evidence and demonstrate that escape from XCI results in sex biases in gene expression, establishing incomplete XCI as a mechanism that is likely to introduce phenotypic diversity. Overall, this updated catalogue of XCI across human tissues helps to increase our understanding of the extent and impact of the incompleteness in the maintenance of XCI.

Cat Personalities

By David Corby Edited by: Arad - Image:Kittyplya03042006.JPG, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1839754

Pet owners no doubt know the personality traits of their animal friends.  The free online article linked here discusses personality types among domestic cats and what these traits can tell us about the well being of the animals and how the information can be used to manage the cats and their environments. The following is from the discussion of the paper, note that while some traits are thought to indicate environmental influences (but I suspect even these likely have some heritable component), Dominance is thought to be more purely biological in mechanism (although there is also the implication that high Extraversion may be as well, with abnormally low Extraversion possibly being, for example, age-related). I'll note from personal experience that guinea pigs also show marked animal-to-animal personality differences when cared for in exactly the same manner and in the same environment.  Dogs also differ markedly, both on a breed and on an individual basis.  From the paper:

The personality profiles of their cats may not only be interesting to cat owners, but may be used to improve welfare, particularly when an individual cat has unusually high or low scores on a factor. Awareness of results being considered extreme on a scale, compared to a sample of 2000+ pet cats, allows the owner to seek advice and consider changes to the environment or management of their cat. Personality profiling may be particularly useful for managing multi-cat households, ideally before obtaining a new cat. The following information provides specific examples.

Cats that score high on Neuroticism (shy) may be stressed and benefit from an assessment of social stress [8] by observing any interactions between the neurotic cat and others (human or non-human animals). These cats may benefit from additional hiding places around the home or access to quiet areas (like cheetahs with high tense-fearful scores [20]). All cats that are allowed to roam outside are at greater risk of disease transmission [42] or injury (road deaths or fights). Cats with low scores for Neuroticism (i.e., they are bold) may travel further (if not confined), compounding this risk.

Cats with high scores for Extraversion (smart, curious, inventive) may need additional stimulation and more complex environmental enrichment to avoid boredom [9], such as extra room to play, additional sensory items or toys, and social interactions with humans and/or other animals [3]. Low scores for Extraversion (clumsiness, aimlessness) may indicate age-related health issues, such as cognitive dysfunction [68], or other health problems, thus requiring further individual assessment from a veterinarian.

High scores on Impulsiveness (erratic, reckless) may also indicate a stressful environment [8, 69], with negative effects on a cat’s health and welfare [70, 71], and owners may need to seek advice from an animal behaviourist to locate the source of stress. Low scores for Impulsiveness are likely to be indicative of cats that are well adjusted to their environment and enjoy routine.

High scores for Agreeableness (friendly) are likely to represent cats that are well adjusted and ‘happy’, potentially serving as a source of enrichment for other cats (see captive elephants (Loxodonta africana) [72] and tigers (Panthera tigris tigris) [73]). Owners typically desire friendly cats [30] for their therapeutic benefits [69], and as a result friendly cats are more likely to be adopted from shelters [2]. Low scores for Agreeableness (irritable/aggressive towards people) may reflect poor socialisation [30], frustration [71], or underlying pain or illness [74].

Further research is needed to understand how extreme scores for the Feline Five factor of Dominance may be used for improving cat welfare. Most of our knowledge about sociality of domestic cats comes from behavioural observations of free-living (feral) colonies, where related adult females cooperate in raising kittens, while there is competition between adult males [8]. High scores for Dominance reflect a cat that is likely to bully other cats in the household, potentially causing stress, aggression or injury [75], with object (food) and social (inter-cat) dominance behaviours observed in situations with forced grouping of cats [29]. This particular personality factor may have a biological basis as oxytocin (a neuropeptide) has been associated with Roughness (consisting of traits irritable, dominant, forceful & moody) in cats [76].

In summary, our Feline Five factors were: Neuroticism, Extraversion, Dominance, Impulsiveness and Agreeableness. Accurate assessment of pet cat personality may help owners manage their cats in a way that optimises cat welfare. Additionally, a greater understanding of cat personality may help owners notice changes in their cat and seek professional assessment by a veterinarian and/or animal behaviour specialist [8, 17, 77].