The testis-determining factor gene (TDF) lies on the Y chromosome and is responsible for initiating male sex determination. SRY is a gene located in the sex-determining region of the human and mouse Y chromosomes and has many of the properties expected for TDF. Sex reversal in XY females results from the failure of the testis determination or differentiation pathways. Some XY females, with gonadal dysgenesis, have lost the sex-determining region from the Y chromosome by terminal exchange between the sex chromosomes or by other deletions. If SRY is TDF, it would be predicted that some sex-reversed XY females, without Y chromosome deletions, will have suffered mutations in SRY. We have tested human XY females and normal XY males for alterations in SRY using the single-strand conformation polymorphism assay and subsequent DNA sequencing. A de novo mutation was found in the SRY gene of one XY female: this mutation was not present in the patient's normal father and brother. A second variant was found in the SRY gene of another XY female, but in this case the normal father shared the same alteration. The variant in the second case may be fortuitously associated with, or predisposing towards sex reversal; the de novo mutation associated with sex reversal provides compelling evidence that SRY is required for male sex determination.

Vascular smooth muscle cells (VSMCs) show pronounced heterogeneity across and within vascular beds, with direct implications for their function in injury response and atherosclerosis. Here we combine single-cell transcriptomics with lineage tracing to examine VSMC heterogeneity in healthy mouse vessels. The transcriptional profiles of single VSMCs consistently reflect their region-specific developmental history and show heterogeneous expression of vascular disease-associated genes involved in inflammation, adhesion and migration. We detect a rare population of VSMC-lineage cells that express the multipotent progenitor marker Sca1, progressively downregulate contractile VSMC genes and upregulate genes associated with VSMC response to inflammation and growth factors. We find that Sca1 upregulation is a hallmark of VSMCs undergoing phenotypic switching in vitro and in vivo, and reveal an equivalent population of Sca1-positive VSMC-lineage cells in atherosclerotic plaques. Together, our analyses identify disease-relevant transcriptional signatures in VSMC-lineage cells in healthy blood vessels, with implications for disease susceptibility, diagnosis and prevention.

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XY females (n = 17) were analysed for mutations in SRY (sex-determining region Y gene), a gene that has recently been equated with the testis determining factor (TDF). SRY sequences were amplified by the polymerase chain reaction (PCR) and analysed by both the single strand conformational polymorphism assay (SSCP) and DNA sequencing. The DNA from two individuals gave altered SSCP patterns; only these two individuals showed any DNA sequence variation. In both cases, a single base change was found, one altering a tryptophan codon to a stop codon, the other causing a glycine to arginine amino acid substitution. These substitutions lie in the high mobility group (HMG)-related box of the SRY protein, a potential DNA-binding domain. The corresponding regions of DNA from the father of one individual and the paternal uncle of the other, were sequenced and found to be normal. Thus, in both cases, sex reversal is associated with de novo mutations in SRY. Combining this data with two previously published reports, a total of 40 XY females have now been analysed for mutations in SRY. The number of de novo mutations in SRY is now doubled to four, adding further strength to the argument that SRY is TDF.

We report on a sex reversed Japanese child with a 46,X,Yp + karyotype, minor dysmorphic features, and no testicular development. The Yp + chromosome was derived by translocation of an Xp fragment (Xp2l-Xp22.3) to Ypll.3. This has resulted in deletion of distal part of the Y chromosome pseudoautosomal region (DXYS15-telomere) and duplication of the X specific region (DXS84-PABX) and proximal part of the pseudoauto-