Deletion of long-range regulatory elements upstream of SOX9 causes campomelic dysplasia

Abstract

Campomelic dysplasia (CD) is a rare, neonatal human chondrodysplasia characterized by bowing of the long bones and often associated with male-to-female sexreversal. Patients present with either heterozygous mutations in the SOX9 gene or chromosome rearrangements mapping at least 50 kb upstream of SOX9. Whereas mutations in SOX9 ORF cause haploinsufficiency, the effects of translocations 5 to SOX9 are unclear. To test whether these rearrangements also cause haploinsufficiency by altering spatial and temporal expression of SOX9, we generated mice transgenic for human SOX9-lacZ yeast artificial chromosomes containing variable amounts of DNA sequences upstream of SOX9. We show that elements necessary for SOX9 expression during skeletal development are highly conserved between mouse and human and reveal that a rearrangement upstream of SOX9, similar to those observed in CD patients, leads to a substantial reduction of SOX9 expression, particularly in chondrogenic tissues. These data demonstrate that important regulatory elements are scattered over a large region upstream of SOX9 and explain how particular aspects of the CD phenotype are caused by chromosomal rearrangements 5 to SOX9.Major diagnostic criteria for the skeletal malformation syndrome, campomelic dysplasia (CD), are angulation of the tibiae and femura, hypoplastic scapulae, nonmineralization of the thoracic pedicles, 11 instead of 12 pairs of ribs, poor ossification of the pelvis, and bilateral talipes equinovaris (1-3). Other skeletal and nonskeletal defects are also associated with the disease, such as micrognathia, cleft palate, and low-set ears. Patients usually die soon after birth of respiratory distress, but the severity of the disease is variable and a few patients survive into adult life. Interestingly, male-to-female sex-reversal occurs in three-quarters of the XY CD patients, whose genitalia can be normal male, female, or ambiguous with various levels of male or female sexual differentiation (1, 3-5). The identification of de novo mutations in the SOX9 gene of sex-reversed CD patients implicated SOX9 as responsible for both skeletal and gonadal phenotypes. Only heterozygous mutations were detected in the patients, suggesting that CD has an autosomal dominant inheritance and haploinsufficiency is the probable cause of the CD and sex-reversal phenotypes (6, 7).The human SOX9 gene maps to chromosome 17q24 (6, 7) and belongs to the SRY-related HMG box (SOX) gene family (8,9). SOX genes encode proteins with greater than 60% similarity at the amino acid level with the SRY DNA-binding domain or HMG box. The SOX genes have been isolated from a variety of organisms, and their role as transcription factors during embryogenesis has been suggested (9-12). SOX9 encodes a putative 509 amino acid protein that contains an HMG box sharing 71% similarity with SRY HMG box and a transactivation domain at the C terminus, suggesting that SOX9 acts as a transcription activator (13,14). Mouse Sox9 gene shares 96% identity with its human homologue (15), indicat...

A study of goat SRY protein expression suggests putative new roles for this gene in the developing testis of a species with long‐lasting SRY expression

“…Because of the greater sensitivity of gene dosage in nonmouse species, the balance between male and female signals should be maintained throughout life in both sexes. This hypothesis is also in line with the results of cross-species transgenesis experiments showing that goat SRY could act as a mouse testicular determinant; i.e., as a Sox9 up-regulator (Pannetier et al, 2006a), but in fact mouse Sry seems to be incapable of up-regulating the human SOX9 gene in mouse testes (Wunderle et al, 1998).…”

Hypoxia‐inducible factor 2α is essential for hypoxic induction of the human articular chondrocyte phenotype

“…Based on our findings, it would be of interest to determine whether SOX9 is a direct target of HIF-2␣ in human articular chondrocytes. However, analysis of recruited factors on the human SOX9 promoter is difficult because of the particular complexity of this promoter (29)(30)(31)(32), with important regulatory elements dispersed over a large region upstream of SOX9 (32). Furthermore, unlike the murine promoter, no HREs have been reported in the human SOX9 promoter (33).…”

Distant regulatory elements in a Sox10‐βGEO BAC transgene are required for expression of Sox10 in the enteric nervous system and other neural crest‐derived tissues

“…Sox9 is regulated by elements at Ͼ350 kb from the start site of transcription (Wunderle et al, 1998). Lack of anticipated expression from the Ϫ2.8Sox10␤ GeoShort construct and the conservation of gene structure between these two gene family members led us to investigate whether Sox10 is also regulated by distant elements.…”