Table 2.

Summary of Molecular Genetic Testing Used in X-Linked Congenital Stationary Night Blindness

Gene 1 / CSNB PhenotypeProportion of X-Linked CSNB Attributed to Mutation of This Gene 2Test MethodVariants Detected 3
NYX / CSNB1A 445%Sequence analysis 5Sequence variants 6, 7
Deletion/duplication analysis 8Exon and whole-gene deletions 7 9
CACNA1F / CSNB2A 1055%Targeted analysis for pathogenic variantsc.3167_3168dupC 11
Sequence analysis 5Sequence variants 6, 7
1.
2.
3.

See Molecular Genetics for information on allelic variants.

4.
5.

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.

6.

Lack of amplification by PCRs prior to sequence analysis can suggest a putative deletion of one or more exons or the entire X-linked gene in a male; confirmation may require additional testing by deletion/duplication analysis.

7.

Sequence analysis of genomic DNA cannot detect deletion of one or more exons or the entire X-linked gene in a heterozygous female.

8.

Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; included in the variety of methods that may be used are: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA) that includes this gene/chromosome segment.

9.
10.
11.

Present in the Dutch-German Mennonite population [Bech-Hansen et al 1998, Boycott et al 2000].

From: X-Linked Congenital Stationary Night Blindness

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