https://www.cell.com/cell/pdf/0092-8674(93)90279-Y.pdf

Circular transcripts of the testis-determining gene Sry in adult mouse testis

Human sex chromosomes evolved from autosomes. Nineteen ancestral autosomal genes persist as differentiated homologs on the X and Y chromosomes. The ages of individual X-Y gene pairs (measured by nucleotide divergence) and the locations of their X members on the X chromosome were found to be highly correlated. Age decreased in stepwise fashion from the distal long arm to the distal short arm in at least four "evolutionary strata." Human sex chromosome evolution was probably punctuated by at least four events, each suppressing X-Y recombination in one stratum, without disturbing gene order on the X chromosome. The first event, which marked the beginnings of X-Y differentiation, occurred about 240 to 320 million years ago, shortly after divergence of the mammalian and avian lineages.

/pdf/four-evolutionary-strata-on-the-human-x-chromosome-jxsxcvjaqg.pdf

Four Evolutionary Strata on the Human X Chromosome

Phylogeny of the SOX family of developmental transcription factors based on sequence and structural indicators.

The Sox gene family consists of a large number of embryonically expressed genes related via the possession of a 79-amino-acid DNA-binding domain known as the HMG box Partial clones for the first three Sox genes (al-a3) were isolated by homology to the HMG box of the testis-determining gene Sry and are now termed Sox-1, Sox-2 and Sox-3, Sox-3 is highly conserved amongst mammalian species and is located on the X chromosome This has led to the proposal that Sry evolved from Sox-3 We present the cloning and sequencing of Sox-1, Sox-2 and Sox-3 from the mouse and show that Sox-3 is most closely relate to Sry We also confirm that mouse Sox-3 is located on the X chromosome between Hprt and Dmd Analysis of the distribution of Sox-3 RNA shows that its main site of expression is in the developing central nervous system, suggesting a role for Sox-3 in neural development Moreover, we demonstrate that Sox-3, as well as Sox-1 and Sox-2, are expressed in the urogenital ridge and that their protein products are able to bind the same DNA sequence motif as Sry in vitro, but with different affinities These observations prompt discussion of an evolutionary link between the genes and support the model that Sry has evolved from Sox-3 However our findings imply that if this is true, then Sry has undergone concomitant changes resulting in loss of CNS expression and altered DNA-binding properties

A comparison of the properties of Sox-3 with Sry and two related genes, Sox-1 and Sox-2

Dense genetic maps of human, mouse, and rat genomes that are based on coding genes and on microsatellite and single-nucleotide polymorphism markers have been complemented by precise gene homolog alignment with moderate-resolution maps of livestock, companion animals, and additional mammal species. Comparative genetic assessment expands the utility of these maps in gene discovery, in functional genomics, and in tracking the evolutionary forces that sculpted the genome organization of modern mammalian species.

/pdf/the-promise-of-comparative-genomics-in-mammals-16sbdcyddp.pdf

The Promise of Comparative Genomics in Mammals

IN mammals, testis determination is under the control of the testis-determining factor borne by the Y chromosome1,2. SRY, a gene cloned from the sex-determining region of the human Y chromosome, has been equated with the testis-determining factor in man3–5 and mouse6,7. We have used a human SRY probe to identify and clone related genes from the Y chromosome of two marsupial species. Comparisons of eutherian and metatherian Y-located SRY sequences suggest rapid evolution of these genes, especially outside the region encoding the DNA-binding HMG box. The SRY homologues, together with the mouse Ubely homologues8, are the first genes to be identified on the marsupial Y chromosome.

Gregory K. Hampikian

Papers

Evolution of sex determination and the Y chromosome: SRY -related sequences in marsupials