Genetic analysis and prenatal diagnosis of 76 Chinese families with X-linked adrenoleukodystrophy

Abstract

Background: Variants in the ATP binding cassette protein subfamily D member 1 (ABCD1) gene are known to cause X-linked adrenoleukodystrophy (X-ALD). This study focused on the characteristics of ABCD1 variants in Chinese X-ALD families and elucidated the value of genetic approaches for X-ALD.

Methods: 68 male probands diagnosed as X-ALD were screened for ABCD1 variants by the Sanger sequencing of polymerase chain reaction (PCR) products and multiplex ligation-dependent probe amplification (MLPA) combined with long-range PCR. Prenatal diagnosis was performed in 20 foetuses of 17 probands' mothers. Descriptive statistics were used to summarise the gene variants and prenatal diagnosis characteristics and outcomes.

Results: This study allowed the identification of 61 variants occurring in 68 families, including 58 single nucleotide variants or small deletion/insertion variants and 3 large deletions. Three probands with no variants detected by next-generation sequencing were found to have variants by PCR-sequencing. Prenatal diagnosis found that 10 of the 20 foetuses had no variants in ABCD1.

Conclusion: PCR primers that do not amplify the pseudogenes must be used for PCR-sequencing. MLPA combined with long-range PCR can detect large deletions and insertions, which are usually undetectable by PCR-sequencing. Prenatal diagnosis could help to prevent the birth of infants with X-ALD.

Keywords: ATP binding cassette transporter-subfamily D and member 1; Chinese cohort; adrenoleukodystrophy; prenatal diagnosis.

FIGURE 1

61 different ABCD1 variants in 68 X‐ALD families. ^aNovel variants are reported here for the first time. ^bVariants are detected in more than one family. P, pathogenic variant; LP, likely pathogenic variant; VUS, variant of uncertain significance; TMD, transmembrane Domain; ABC, ATP Binding Cassette

FIGURE 2

The results of long‐range PCR and Sanger sequencing. (a) Long‐range PCR is used in pedigree X53. The patient X53 and his mother are checked in lanes X53 and X53 M, respectively. The negative control and DNA marker are shown in lanes C and M. Lane C only has one band (1791bp). X53 only has one band (385bp) and his mother has two bands (1791bp and 385bp). (b) Sanger sequencing results of patient X53