Mutational and Protein Analysis of Patients and Heterozygous Women With X-linked Adrenoleukodystrophy

Am J Hum Genet. 1996 Jun;58(6):1135-44.

Abstract

X-linked adrenoleukodystrophy (ALD), a neurodegenerative disorder associated with impaired beta-oxidation of very-long-chain fatty acids (VLCFA), is due to mutations in a gene encoding a peroxisomal ATP-binding cassette (ABC) transporter (ALD protein [ALDP]). We analyzed the open reading frame of the ALD gene in 44 French ALD kindred by using SSCP or denaturing gradient-gel electrophoresis and studied the effect of mutations on ALDP by immunocytofluorescence and western blotting of fibroblasts and/or white blood cells. Mutations were detected in 37 of 44 kindreds and were distributed over the whole protein-coding region, with the exception of the C terminus encoded in exon 10. Except for two mutations (delAG1801 and P560L) observed four times each, nearly every ALD family has a different mutation. Twenty-four of 37 mutations were missense mutations leading to amino acid changes located in or close to putative transmembrane segments (TMS 2, 3, 4, and 5), in the EAA-like motif and in the nucleotide fold of the ATP-binding domain of ALDP. Of 38 ALD patients tested, 27 (71%) lacked ALDP immunoreactivity in their fibroblasts and/or white blood cells. More than half of missense mutations studied (11 of 21) resulted in a complete lack of ALDP immunoreactivity, and six missense mutations resulted in decreased ALDP expression. The fibroblasts and/or white blood cells of 15 of 15 heterozygous carrier from ALD kindred with no ALDP showed a mixture of positive- and negative-ALDP immunoreactivity due to X-inactivation. Since 5%-15% of heterozygous women have normal VLCFA levels, the immunodetection of ALDP in white blood cells can be applicable in a majority of ALD kindred, to identify heterozygous women, particularly when the ALD gene mutation has not yet been identified.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily D, Member 1
  • ATP-Binding Cassette Transporters / genetics*
  • Addison Disease / genetics
  • Adolescent
  • Adrenoleukodystrophy / genetics*
  • Alternative Splicing
  • Amino Acid Sequence
  • Base Sequence
  • Child
  • Child, Preschool
  • DNA / blood
  • DNA / chemistry
  • DNA / isolation & purification
  • DNA Primers
  • Electrophoresis
  • Exons
  • Female
  • Fibroblasts
  • Frameshift Mutation*
  • Genetic Carrier Screening
  • Humans
  • Leukocytes
  • Male
  • Membrane Proteins / genetics*
  • Molecular Sequence Data
  • Point Mutation*
  • Polymerase Chain Reaction
  • Polymorphism, Single-Stranded Conformational
  • X Chromosome*

Substances

  • ABCD1 protein, human
  • ATP Binding Cassette Transporter, Subfamily D, Member 1
  • ATP-Binding Cassette Transporters
  • DNA Primers
  • Membrane Proteins
  • DNA