the origin of sex chromosomes in...

THE ORIGIN OF SEX

CHROMOSOMES IN

HUMANS

Miguel Ángel Rosales Motos

Master in Advanced Genetics

Genomics

11th of December, 2019

INDEX

1. Introduction

2. Origin of human sex chromosomes

3. Organization of human sex chromosomes

4. Conclusions

5. References

INTRODUCTIONSEX DETERMINATION

ENVIRONMENTAL SEX DETERMINATION GENETICALLY CONTROLLED SEX DETERMINATION


ENVIRONMENTAL SEX DETERMINATION GENETICALLY CONTROLLED SEX DETERMINATION

Sexual determination based on the

temperature


ENVIRONMENTAL SEX DETERMINATION

GENETICALLY CONTROLLED SEX DETERMINATION

XY/XX


temperature




XY/XX ZW/ZZ


temperature




XY/XX ZW/ZZ

X0/XX or Z0/ZZ


temperature




XY/XX ZW/ZZ

X0/XX or Z0/ZZ Neo-sex chromosomes


temperature




XY/XX ZW/ZZ

X0/XX or Z0/ZZ Neo-sex chromosomes

Ring / chain systemSexual determination based on the

temperature


Graves et al., 2015

Vertebrates sex

chromosomes and

phylogeny

SEX CHROMOSOMES IN HUMANS

➢ Testis-determining factor in

the proto-Y; beneficial

genes around it

➢ Recombination is

suppressed

➢ The two X chromosomes

recombine normally

Livernois et al., 2012


➢ Recombination is further

suppressed

➢ Proto-Y degrades; loss of

function of some genes

➢ Upregulation in males and

females



➢ More upregulation in males

➢ Upregulation and

downregulation in females

➢ Genes with male-specific

function



➢ Restriction of recombination

➢ Degeneration of the Y

➢ Male-specific role

➢ Overexpression and

inactivation of homologous

regions in females



➢ Addition of an autosomal

segment



➢ Differentiation/loss of

genes on Y

➢ Upregulation of the X copy

➢ Suppression of

recombination into the

added segment


ORGANIZATION OF HUMAN SEX CHROMOSOMES

➢X-conserved region (XCR)

➢X-added region (XAR)

➢Pseudoautosomal region (PAR)

➢S1-S5: strata

X CHROMOSOME

Ellegreen et al., 2011

ORGANIZATION OF HUMAN SEX CHROMOSOMES

➢Pseudoautosomal regions

➢Male-specific region on Y (MRY):

➢Ampliconic regions

➢X-degenerated regions

➢X-transposed region

Y CHROMOSOME

Ellegreen et al., 2011

CONCLUSIONS

➢ Sex chromosomes originated from a pair of autosomes.

➢ Sex chromosomes have evolved independently many times in different lineages,they show common features (evolutionary convergence).

➢ In vertebrates, sex chromosome differentiation has followed the same path.

➢ The presence of a heterogametic sex leads to degeneration of one of the sexchromosomes.

➢Sex chromosome differentiation can be used in the phylogeny.

REFERENCES

Ellegren, H. (2011, March). Sex-chromosome evolution: Recent progress and the influence of male and female heterogamety. Nature Reviews Genetics, Vol. 12, pp. 157–166. https://doi.org/10.1038/nrg2948

Graves, J. A. M. (2016, January 1). Evolution of vertebrate sex chromosomes and dosage compensation. Nature Reviews Genetics, Vol. 17, pp. 33–46. https://doi.org/10.1038/nrg.2015.2

Hughes, J. F., & Rozen, S. (2012). Genomics and Genetics of Human and Primate Y Chromosomes. Annual Review of Genomics and Human Genetics, 13(1), 83–108. https://doi.org/10.1146/annurev-genom-090711-163855

Livernois, A. M., M Graves, J. A., & Waters, P. D. (2011). The origin and evolution of vertebrate sex chromosomes and dosage compensation AM Livernois, JAM Graves and PD Waters. 108. https://doi.org/10.1038/hdy.2011.106

Soh, Y. Q. S., Alföldi, J., Pyntikova, T., Brown, L. G., Graves, T., Minx, P. J., Page, D. C. (2014). Sequencing the mouse y chromosome reveals convergent gene acquisition and amplification on both sex chromosomes. Cell, 159(4), 800–813. https://doi.org/10.1016/j.cell.2014.09.052

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