Heterogenous band 3 deficiency in hereditary spherocytosis related to different band 3 gene defects

Abstract

Summary. Among 80 hereditary spherocytosis (HS) kindreds studied using denaturing electrophoretic separation of solubilized eythrocyte membrane proteins, we recognized three prominent subsets: HS with isolated spectrin deficiency, HS with combined spectrin and ankyrin deficiency, and HS with band 3 deficiency. These three subsets represent more than 80% of the HS kindreds studied. In this study, eight dominant HS kindreds with band 3 deficiency were investigated for band 3 mutations. In three of these kindreds, linkage analyses confirmed the band 3 gene as the culprit gene. In an attempt to identify the responsible mutations, denaturing gradient gel electrophoresis (DGGE) was used to explore the coding exons (exons 2-20) of band 3 gene. Five different mutations were found in the eight kindreds. In five kindreds we identified substitutions of highly conserved residues, positioned at boundaries of putative transmembrane segments: a C → T substitution at codon 490 changed arginine (CGC) to cysteine (TGC) in three kindreds, a C → T substitution at codon 837 changed threonine (ACG) to methionine (ATG) in two kindreds. In the sixth kindred a G deletion was found in a stretch of five G starting at position 1475, leading to a stop codon either at position 1527 or 1565. In the seventh kindred a T deletion at position 1600 resulted in a stop codon at position 1733 and in the last kindred a T deletion was identified at position 355, leading to a stop codon at position 447. The mutant transcript was present in HS patients bearing missense mutations, whereas only the normal transcript was found in HS patients with frameshift mutations. In the latter group the mean decrease in membrane band 3 content was significantly lower, leading to speculation that missense mutations may have some sort of dominant negative effect.

A new ankyrin mutation (ANK1 EXON E9X) causing severe hereditary spherocytosis in the neonatal period

“…This is consistent to genetic studies in which in most sporadic cases a large number of de novo mutations arises in the maternal germ line [4].…”

“…Ankyrin is the principal binding site for spectrin on the red cell membrane; as a result, ankyrin deficiency leads to decreased incorporation of spectrin on the membrane. In approximately one-third of patients with ankyrin deficiency, one ankyrin mRNA allele is virtually missing due to deletion, frameshift, or nonsense mutations that alter transcription, processing, or stability of ankyrin mRNA [1,4,5]. Other ankyrin mutations in dominant hereditary spherocytosis include truncated variants and one nonexpressed isoform [6,7].…”

Ubiquitylation-independent ER-associated degradation of an AE1 mutant associated with dominant hereditary spherocytosis in cattle

“…Previous studies in patients or animals with AE1 mutations failed to demonstrate the presence of mutant AE1 protein in their red-cell membranes. This finding was partly explained, particularly in the case of the nonsense mutations, by the absence of mutant transcripts in the reticulocytes of patients (Jarolim et al, 1996;Jenkins et al, 1996;Dhermy et al, 1997). However, although HS with AE1 deficiency is usually homogeneous with regard to the clinical and biochemical Various mutations in the AE1 (anion exchanger 1, band 3) gene cause dominant hereditary spherocytosis, a common congenital hemolytic anemia associated with deficiencies of AE1 of different degrees and loss of mutant protein from red blood cell membranes.…”

“…features within a given family, several investigators report that the extent to which AE1 protein levels are reduced differs depending on the mutation (Alloisio et al, 1996;Alloisio et al, 1997;Dhermy et al, 1997). Moreover, mice heterozygous for a disrupted AE1 gene exhibit only a mild (20%) deficiency of AE1 protein (Peters et al, 1996), possibly reflecting the amount of the protein produced from the normal allele.…”

“…Various mutations of the human AE1 (SLC4A1) gene, including missense, nonsense and frameshift mutations, have been reported to cause dominant HS, which is associated with a 20-40% reduction in AE1 protein levels in the red-cell membrane (Jarolim et al, 1994;Jarolim et al, 1996;Alloisio et al, 1996;Alloisio et al, 1997;Dhermy et al, 1997;Jenkins et al, 1996;Tanner, 2002). Total AE1 deficiency in cattle in the homozygous state for a nonsense mutation R664X, corresponding to a premature termination at residue R646 in human AE1, also showed atypical spherocytosis with marked membrane instability (Inaba et al, 1996;Inaba, 2000).…”