Table 1.

Summary of Molecular Genetic Testing Used in Peters Plus Syndrome

Gene 1Test MethodVariants Detected 2Variant Detection Frequency by Test Method 3
B3GLCTSequence analysis 4Sequence variants 527% (9/26) 6
100% (20/20) 7
Deletion/duplication analysis 8Partial-, whole-, and contiguous-gene deletions2/20 7, 9
1.
2.

See Molecular Genetics for information on allelic variants.

3.

The ability of the test method used to detect a variant that is present in the indicated gene

4.

Examples of pathogenic variants detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice-site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

5.

Most affected individuals tested to date are homozygous for a splice-site variant in intron 8 (c.660+1G>A) [Lesnik Oberstein et al 2006]. However, several other loss-of-function variants have been identified, including pathogenic missense variants located in the putative catalytic domain of the enzyme.

6.

As identified by the Laboratory of Diagnostic Genome Analysis, Leiden, The Netherlands. Note: This is a clinically heterogeneous group.

7.

As identified by Lesnik Oberstein et al [2006]. This cohort is clinically well described.

8.

Testing that identifies deletions/duplications not readily detectable by sequence analysis of genomic DNA; a variety of methods including quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), or targeted chromosomal microarray analysis (gene/segment-specific) may be used. A full chromosomal microarray analysis that detects deletions/duplications across the genome may also include this gene/segment.

9.

Lesnik Oberstein et al [2006] described two brothers with a ~1.5-Mb contiguous gene deletion on their maternal allele, including B3GLCT. The proximal deletion breakpoint is between exons 7 and 8 of B3GLCT; the distal breakpoint is between exons 13 and 14 of BRCA2. Haldeman-Englert et al [2009] also reported a large deletion including the whole B3GLCT gene. The paternal allele harbored a pathogenic single-nucleotide variant. Within the Laboratory of Diagnostic Genome Analysis, Leiden, The Netherlands, a heterozygous deletion of only exon 7 was identified; the other allele harbored the common intron 8 splice-site variant [Author, personal communication].

From: Peters Plus Syndrome

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