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. 2007 Dec;81(6):1169-85.
doi: 10.1086/522090. Epub 2007 Oct 22.

Deletions at the SOX10 gene locus cause Waardenburg syndrome types 2 and 4

Nadege Bondurand  1 , Florence Dastot-Le Moal, Laure Stanchina, Nathalie Collot, Viviane Baral, Sandrine Marlin, Tania Attie-Bitach, Irina Giurgea, Laurent Skopinski, William Reardon, Annick Toutain, Pierre Sarda, Anis Echaieb, Marilyn Lackmy-Port-Lis, Renaud Touraine, Jeanne Amiel, Michel Goossens, Veronique Pingault
Affiliations

Deletions at the SOX10 gene locus cause Waardenburg syndrome types 2 and 4

Nadege Bondurand et al. Am J Hum Genet. 2007 Dec.

Abstract

Waardenburg syndrome (WS) is an auditory-pigmentary disorder that exhibits varying combinations of sensorineural hearing loss and abnormal pigmentation of the hair and skin. Depending on additional symptoms, WS is classified into four subtypes, WS1-WS4. Absence of additional features characterizes WS2. The association of facial dysmorphic features defines WS1 and WS3, whereas the association with Hirschsprung disease (aganglionic megacolon) characterizes WS4, also called "Waardenburg-Hirschsprung disease." Mutations within the genes MITF and SNAI2 have been identified in WS2, whereas mutations of EDN3, EDNRB, and SOX10 have been observed in patients with WS4. However, not all cases are explained at the molecular level, which raises the possibility that other genes are involved or that some mutations within the known genes are not detected by commonly used genotyping methods. We used a combination of semiquantitative fluorescent multiplex polymerase chain reaction and fluorescent in situ hybridization to search for SOX10 heterozygous deletions. We describe the first characterization of SOX10 deletions in patients presenting with WS4. We also found SOX10 deletions in WS2 cases, making SOX10 a new gene of WS2. Interestingly, neurological phenotypes reminiscent of that observed in WS4 (PCWH syndrome [peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, WS, and Hirschsprung disease]) were observed in some WS2-affected patients with SOX10 deletions. This study further characterizes the molecular complexity and the close relationship that links the different subtypes of WS.

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Figures

Figure 1.
Figure 1.
SOX10 deletions in patients presenting with the classic form of WS4 or PCWH. A, Schematic representation of the three deletions identified by QMF-PCR. The scheme on the top indicates the SOX10 gene structure (an approximate scale is shown on the right). SOX10 coding sequence (exons 3–5) is indicated with black boxes, and noncoding exonic sequence is indicated with white boxes. Arrowheads indicate the position of the segments analyzed by QMF-PCR (P1–P9; see table 2 for corresponding primer sequences). They include the downstream adjacent POLR2F gene (gray box) and four short regions located up to 50 kb upstream of SOX10, indicated by dark lines and labeled S1–S4. QMF-PCR results for patients 1–3 are indicated: + = not deleted; − = deleted. The phenotypes are indicated on the left. B, Schematic representation (top) and electropherogram (bottom) of the deletion breakpoint region of patient 1. The size of the deletion and the nucleotidic localization of the breakpoint are indicated on the diagram. The 3 inserted nt are boxed. C, Hybridization pattern of patients 2 and 3 with use of BAC clone RP5-1039K5 encompassing the SOX10 locus (indicated at the top of panel A). The BAC clone RP5-1039K5 is shown in red, and the control probe (RP1-41P2) is shown in green. The normal chromosome 22 is indicated by an arrow, and the deleted chromosome 22 is indicated by an arrowhead.
Figure 2.
Figure 2.
Functional consequences of the p.Val92Leu (V92L) mutation. A, Amino acid sequence comparison of the region immediately preceding the HMG domain of SOX10 proteins across evolution and of SOX subgroup E proteins (human sequences). Gaps are indicated by blanks. The first part of the HMG domain is boxed, and the amino acid substitution V92L from patient 3 is indicated by an arrow. SOX10 sequence reference numbers: human (accession number NP_008872.1), mouse (XP_128139.4), chicken (NP_990123.1), fugu (NP_001072112.1), zebrafish (NP_571950.1), human SOX8 (NP_055402.2), and human SOX9 (NP_000337.1). B, Subcellular localization of wild-type SOX10 and p.Val92Leu mutant. HeLa cells were transfected with pECE-SOX10 (WT) or mutant (V92L) constructs for 24 h, were fixed, and were immunostained for SOX10. Cultures were counterstained with DAPI. C and D, Transactivation capacities of SOX10 proteins. The MITF promoter (pMITF) (C) or the GJB1 (pCx32) promoter (D) luciferase reporters were transfected in Hela cells in combination with wild-type (WT) or mutant SOX10 proteins (V92L, E189X, 482ins6, and Y313X), and/or PAX3 (C) or EGR2 (D). Reporter-gene activations are presented as fold induction relative to the empty expression vector (pECE). Results represent the mean±SEM from six experiments, each performed in duplicate. Insets in C and D show a schematic representation of relative localization of SOX10 (white boxes), PAX3 (striped circles) or EGR2 (striped triangles) binding sites on MITF or GJB1 (Cx32) promoters.
Figure 3.
Figure 3.
Determination of the extent of large deletions in patients with PCWH. Schematic representation of the deletions in patients 2 and 3 was determined by FISH (A) or QMF-PCR (B). A, Representative FISH results. The names of the BACs used for hybridization are indicated on each panel. B, Scheme with the names, positions, and orientation of genes located proximal or distal of SOX10. An approximate scale is shown. BACs used for FISH experiments are shown on the left, and segments analyzed by QMF-PCR are indicated by arrowheads (see table 4 for corresponding primer sequences). QMF-PCR results of patients 2 and 3 are indicated next to the corresponding fragments: + = not deleted; − = deleted.
Figure 4.
Figure 4.
SOX10 deletions in patients presenting with WS2. A, Schematic representation of the five deletions identified by QMF-PCR. The top scheme indicates the SOX10 gene structure and QMF-PCR experiment results (+ = not deleted; − = deleted), as described in figure 1. B and D, Schematic representation (top) and electropherograms (bottom) of the breakpoint deletion region of patient 4 (B) and patient 5 (D) and their relatives. The sizes of the deletions and the breakpoints are indicated on the scheme. C, PCR covering exon 3 and intron-exon boundaries, with the use of DNA from patient 4, his brother, his mother, and his father, extracted from leukocytes (L), buccal cells (B), uroepithelial cells (U), and hair roots (H). The normal band is indicated by an arrow, and the mutant allele is indicated by an arrowhead. Note the faint mutant band in the mother’s uroepithelial cells. E, Representative FISH result obtained for patient 8 with probe RP5-1039K5 encompassing the SOX10 locus (indicated on the top scheme of panel A). The BAC clone RP5-1039K5 is shown in red, and the control probe (RP1-127L4) is shown in green. The normal chromosome 22 is indicated by an arrow, and the deleted chromosome 22 is indicated by an arrowhead.
Figure 5.
Figure 5.
Determination of the extent of large deletions in WS2. Schematic representation of the deletions in patients 6, 7, and 8 was determined by FISH (A) or QMF-PCR (B), as described in figure 3. Only the first nondeleted or partially deleted BACs are shown in panel A.
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References

Web Resources

    1. BACPAC Resources, http://bacpac.chori.org/
    1. GenBank, http://www.ncbi.nlm.nih.gov/Genbank/ (for accession numbers NC_000021.7, NC_000023.9, and NC_000022.9)
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