Alternative titles; symbols
HGNC Approved Gene Symbol: EPB41
Cytogenetic location: 1p35.3 Genomic coordinates (GRCh38): 1:28,887,100-29,120,041 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 1p35.3 | Elliptocytosis-1 | 611804 | Autosomal dominant; Autosomal recessive | 3 |
Conboy et al. (1986) reported the molecular cloning and characterization of human erythrocyte protein 4.1 cDNA and the complete amino acid sequence of the protein. Probes prepared from the cloned erythrocyte protein 4.1 cDNA hybridized with distinct mRNA species from a wide variety of nonerythroid tissues, including brain, liver, placenta, pancreas, and intestine, implying substantial homology between erythroid and nonerythroid protein 4.1. Brain protein 4.1, also known as synapsin I (313440), is the best characterized of the nonerythroid forms.
Tang et al. (1988) compared nucleotide sequences of mRNA encoding erythroid and lymphoid protein 4.1 isoforms. The lymphoid protein 4.1 isoforms exhibited several nucleotide sequence motifs that appeared either to be inserted into or deleted from the mRNA by alternative splicing of a common mRNA precursor. One of the motifs, located within the spectrin-actin binding domain, was found only in erythroid cells and was specifically produced during erythroid cell maturation. Conboy et al. (1988) demonstrated that alternative splicing accounts for multiple isoforms of protein 4.1 in red cells. In his Figure 2, Conboy (1993) provided a map of the alternative splicing of protein 4.1 mRNA, emphasizing the total chromosome relative to many combinatorial splicing possibilities among the exons of the EPB41 gene. There are, furthermore, 2 AUG initiation codons, 1 of which accounts for an N-terminal extension on the 80-kD gene product.
By tissue screening, Baklouti et al. (1997) examined the complex pattern of alternative splicing variants of the protein 4.1 gene. They noted that many splicing variations occur in the spectrin/actin binding (SAB) domain. In particular, they found a 51-bp exon that was expressed almost exclusively in muscle.
By genomic sequence analysis, Baklouti et al. (1997) determined that 22 exons spanning approximately 200 kb contain the entire erythroid and nonerythroid coding sequences of the human protein 4.1 gene.
The protein 4.1 gene was mapped to chromosome 1pter-p32 (Conboy et al. (1985, 1986)) by hybridization to chromosomes sorted onto nitrocellulose filters using a fluorescence-activated cell sorter. Studies of translocations also localized the gene to chromosome 1pter-p32, the region of the Rh gene (Kan, 1986). Thus, it seemed certain that the protein 4.1 gene is mutant in Rh-linked elliptocytosis-1 (EL1; 611804).
Tang and Tang (1991) concluded that the EL1 gene is located in band 1p34.2-p33 on the basis of the FLpter value (the fractional length of the total chromosome relative to the terminus of the short arm).
Parra et al. (1998) stated that the EPB41 gene is located on chromosome 1p33-p32.
Bahary et al. (1991) assigned the mouse Epb41 gene to chromosome 4.
The red cell membrane cytoskeletal network consists of spectrin (bands 1 and 2; see 182860 and 182870), actin (band 5; see 102630), and protein 4.1. Actin and protein 4.1 interact with spectrin at the junction of spectrin heterotetramers. The resulting complex plays a critical role in erythrocyte shape and deformability. (The protein band nomenclature given here is that of Fairbanks et al., 1971.) Correas et al. (1986) determined the complete primary structure of the functional site of protein 4.1 involved in spectrin-actin associations. Antibodies against 2 different synthetic peptides of this portion of the protein inhibited association between protein 4.1, spectrin, and actin.
Ponthier et al. (2006) stated that the 4.1R protein in early erythroid progenitors, derived from transcripts in which exon 16 is skipped, exhibits low affinity for spectrin and actin. In contrast, late-stage erythroblasts include exon 16 and express a high-affinity isoform. This stage-specific repression of exon 16 inclusion is mediated in part by the binding of HNRNPA/B (602688) proteins to exonic splicing silencer elements located within the exon. Ponthier et al. (2006) also found that FOX1 (A2BP1; 605104) and FOX2 (RBM9; 612149) stimulate exon 16 splicing into a 4.1R pre-mRNA minigene via specific binding to UGCAUG splicing enhancer motifs downstream of exon 16.
Conboy et al. (1986) showed by Southern blot analysis of genomic DNA from an Algerian family that in affected members the mutant protein 4.1 gene had a DNA rearrangement upstream from the initiation codon for translation. The mRNA from the mutant gene was aberrantly spliced.
Lambert et al. (1988) reported an elliptocytosis family in which an apparent rearrangement of the coding region of the protein 4.1 gene led to restriction fragment length polymorphism when DNA was tested using a fragment of the cDNA that encompassed the coding region of the gene.
McGuire et al. (1988) described a distinct variant of protein 4.1 in each of 3 families with elliptocytosis. Affected members of family C, of Italian ancestry, had red cells with reduced content of protein 4.1 of normal molecular mass (approximately 80 kD).
Tan et al. (2005) found that the EPB41 and EPB41L3 (605331) genes from fish, bird, amphibian, and mammalian genomes exhibit shared features, including alternative first exons and differential splicing acceptors in exon 2. In all cases, the most 5-prime exon, exon 1A, splices exclusively to a weaker internal acceptor site in exon 2, skipping a fragment designated exon 2-prime. Conversely, alternative first exons 1B and 1C always splice to the stronger first acceptor site, retaining exon 2-prime. These correlations were independent of cell type or species of origin. Since exon 2-prime contains a translation initiation site, splice variants generate protein isoforms with distinct N termini. Tan et al. (2005) calculated that coupling between upstream promoters and downstream splicing in EPB41 and EBP41L3 has been conserved for at least 500 million years.
The complex EPB41 gene on human chromosome 1p encodes a diverse family of protein 4.1R isoforms. The prototypic 80-kD 4.1R in mature erythrocytes is a key component of the erythroid membrane skeleton that regulates red cell morphology and mechanical stability. To study the function of 4.1R in nucleated cells, Shi et al. (1999) generated mice with complete deficiency of all 4.1R protein isoforms. These 4.1R-null mice were viable, with moderate hemolytic anemia but no gross abnormalities. Platelet morphology and function were essentially normal. Nonerythroid 4.1R expression patterns revealed focal expression in specific neurons in the brain and in select cells of other major organs, challenging the view that 4.1R expression is widespread among nonerythroid cells.
Epb41-knockout mice have fragmented red blood cells that lack glycophorin C (GPC; see 110750). In Epb41-null murine erythroblasts, Salomao et al. (2010) found that GPC distributed exclusively to the nuclei, whereas in enucleating erythroblasts from wildtype bone marrow, GPC partitioned almost exclusively to nascent reticulocytes, with little or no GPC observed in plasma membranes of extruding nuclei. In contrast, glycophorin A (GPA; 617922) partitioning was not perturbed, and GPA sorted to nascent reticulocytes in both Epb41-null and wildtype enucleating erythroblasts. The findings indicated that GPC deficiency in Epb41-null erythroblasts is attributable to markedly abnormal protein partitioning during enucleation, and suggested that reticulocytes in hereditary elliptocytosis may differ from normal reticulocytes in their biophysical properties of membrane cohesion or membrane deformability. The results also showed that cytoskeletal attachments are an important factor in regulating transmembrane protein sorting to reticulocytes.
This mutation was first reported by Feo et al. (1980) and Tchernia et al. (1981) in homozygotes and heterozygotes and by Alloisio et al. (1985) in heterozygotes. In this form of elliptocytosis (EL1; 611804), Takakuwa et al. (1986) demonstrated restitution of normal membrane stability by incorporation of purified protein 4.1 into deficient red cells by exchange hemolysis.
In an Algerian family with hereditary elliptocytosis caused by deficiency of erythroid protein 4.1 (described by Tchernia et al., 1981; defect partially characterized by Conboy et al., 1986), Conboy et al. (1993) delineated the defect by study of erythroid and nonerythroid cells in 1 of the homozygously affected sibs. The molecular lesion was shown to involve deletion of the downstream AUG initiation codon in 4.1 mRNA, thus leading to the absence of protein 4.1 in red cells. In contrast, isoforms that use the upstream AUG were detected in nonerythroid cells, thus explaining the absence of manifestations in other organ systems. The lesion consisted of a 318-nucleotide deletion that encompassed the downstream AUG but left the upstream AUG intact. Normally, multiple protein 4.1 isoforms are expressed in a variety of tissues through complex alternative pre-mRNA splicing events, one function of which is to regulate use of 2 alternative translation initiation signals. Late erythroid cells express mainly the downstream initiation site for synthesis of prototypic 80-kD isoforms; nonerythroid cells in addition use an upstream site to encode higher molecular mass isoform(s).
In affected members of family N of Scottish-Irish descent, McGuire et al. (1988) found heterozygosity for a high molecular weight form of protein 4.1 at approximately 95 kD, referred to as protein 4.1(95). Marchesi et al. (1990) described the site and nature of the insertion resulting in protein 4.1(95) and the functional consequences of the mutation. The elliptocytosis (EL1; 611804) was mild without anemia. Protein 4.1(95) was found to contain an insertion of about 15 kD adjacent to the spectrin/actin domain of the protein comprised, at least in part, of repeated sequence. Conboy et al. (1990) used polymerase chain reaction (PCR) techniques to clone and sequence mutant reticulocyte mRNAs and correlate the duplication end points with exon boundaries of the gene. Protein 4.1(95) mRNA was found to encode a protein with 2 spectrin/actin binding domains by virtue of a 369-nucleotide duplication from the codon for lys407 to that for gln529.
In affected members of family G, of Italian descent, McGuire et al. (1988) found heterozygosity for normal 4.1(80) and 2 low molecular weight forms of protein 4.1 at about 68 and 65 kD, referred to as protein 4.1(68/65). The mutation was associated with moderate elliptocytosis (EL1; 611804) and anemia. Protein 4.1(68/65) was found to lack the entire spectrin/actin binding domain. Conboy et al. (1990) demonstrated that protein 4.1(68/65) mRNA lacked sequences encoding the functionally important spectrin-actin binding domain due to a 240-nucleotide deletion spanning the codons for lys407 to gly486. Marchesi et al. (1990) described the site and nature of the deletions resulting in protein 4.1(68/65) and the functional consequences of these mutations.
Dalla Venezia et al. (1992) studied homozygous hereditary elliptocytosis (EL1; 611804) in a Spanish patient whose parents were second cousins. He had had intermittent jaundice and pallor since birth. During aplastic crisis at the age of 31 years, the spleen was very large and was removed and cholecystectomy for gallstones was also performed. Remarkable hematologic improvement followed. The mother of the propositus was healthy, although her blood smear showed elliptocytosis; the father was deceased. Glycophorin C was sharply reduced. This finding, as in other homozygous elliptocytosis cases, indicates that protein 4.1 stabilizes glycophorin C (110750) in the membrane. Spectrin and actin were slightly, yet significantly, diminished. Dalla Venezia et al. (1992) demonstrated an abnormality in 4.1 cDNA, specifically an AUG-to-AGG transversion in the downstream translation initiation codon, changing methionine to arginine. No obvious disorders were noted in cell types other than red cells or possibly sperm cells. The propositus, born in 1948, had infertility associated with azoospermia and a right ureterocele. Whereas heterozygous 4.1(-) HE accounts for one-fourth to one-third of all HE in Caucasians, the incidence of homozygous 4.1(-) HE was, in the opinion of Dalla Venezia et al. (1992), lower than anticipated. They suggested that some 4.1(-) HE alleles may not be viable in the homozygous state by virtue of affecting all isoforms of the protein and leaving all cells deficient in protein 4.1. This was the first identification of a specific point mutation, which was called protein 4.1 Madrid.
Garbarz et al. (1995) identified a heterozygous mutation in the downstream translation start site (ATG-to-ACG; met1-to-thr) of the EPB41 gene in affected members of a family with elliptocytosis (EL1; 611804). The mutation was designated protein 4.1 Lille.
Alloisio, N., Morle, L., Dorleac, E., Gentilhomme, O., Bachir, D., Guetarni, D., Colonna, P., Bost, M., Zouaoui, Z., Roda, L., Roussel, D., Delaunay, J. The heterozygous form of 4.1(-) hereditary elliptocytosis [the 4.1(-) trait]. Blood 65: 46-51, 1985. [PubMed: 3965051]
Bahary, N., Zorich, G., Pachter, J. E., Leibel, R. L., Friedman, J. M. Molecular genetic linkage maps of mouse chromosomes 4 and 6. Genomics 11: 33-47, 1991. [PubMed: 1684952] [Full Text: https://doi.org/10.1016/0888-7543(91)90099-z]
Baklouti, F., Huang, S.-C., Vulliamy, T. J., Delaunay, J., Benz, E. J., Jr. Organization of the human protein 4.1 genomic locus: new insights into the tissue-specific alternative splicing of the pre-mRNA. Genomics 39: 289-302, 1997. [PubMed: 9119366] [Full Text: https://doi.org/10.1006/geno.1996.4512]
Conboy, J. G., Chan, J., Mohandas, N., Kan, Y. W. Multiple protein 4.1 isoforms produced by alternative splicing in human erythroid cells. Proc. Nat. Acad. Sci. 85: 9062-9065, 1988. [PubMed: 3194408] [Full Text: https://doi.org/10.1073/pnas.85.23.9062]
Conboy, J. G., Chasis, J. A., Winardi, R., Tchernia, G., Kan, Y. W., Mohandas, N. An isoform-specific mutation in the protein 4.1 gene results in hereditary elliptocytosis and complete deficiency of protein 4.1 in erythrocytes but not in nonerythroid cells. J. Clin. Invest. 91: 77-82, 1993. [PubMed: 8423235] [Full Text: https://doi.org/10.1172/JCI116203]
Conboy, J. G., Mohandas, N., Wang, C., Tchernia, G., Shohet, S. B., Kan, Y. W. Molecular cloning and characterization of the gene coding for red cell membrane skeletal protein 4.1. (Abstract) Blood 66 (suppl. 1): 31A, 1985.
Conboy, J. G. Structure, function, and molecular genetics of erythroid membrane skeletal protein 4.1 in normal and abnormal red blood cells. Semin. Hemat. 30: 58-73, 1993. [PubMed: 8434260]
Conboy, J., Kan, Y. W., Shohet, S. B., Mohandas, N. Molecular cloning of protein 4.1, a major structural element of the human erythrocyte membrane skeleton. Proc. Nat. Acad. Sci. 83: 9512-9516, 1986. [PubMed: 3467321] [Full Text: https://doi.org/10.1073/pnas.83.24.9512]
Conboy, J., Marchesi, S., Kim, R., Agre, P., Kan, Y. W., Mohandas, N. Molecular analysis of insertion/deletion mutations in protein 4.1 in elliptocytosis. II. Determination of molecular genetic origins of rearrangements. J. Clin. Invest. 86: 524-530, 1990. [PubMed: 2384598] [Full Text: https://doi.org/10.1172/JCI114739]
Conboy, J., Mohandas, N., Tchernia, G., Kan, Y. W. Molecular basis of hereditary elliptocytosis due to protein 4.1 deficiency. New Eng. J. Med. 315: 680-685, 1986. [PubMed: 3755799] [Full Text: https://doi.org/10.1056/NEJM198609113151105]
Correas, I., Speicher, D. W., Marchesi, V. T. Structure of the spectrin-actin binding site of erythrocyte protein 4.1. J. Biol. Chem. 261: 13362-13366, 1986. [PubMed: 3531202]
Dalla Venezia, N., Gilsanz, F., Alloisio, N., Ducluzeau, M.-T., Benz, E. J., Jr., Delaunay, J. Homozygous 4.1(-) hereditary elliptocytosis associated with a point mutation in the downstream initiation codon of protein 4.1 gene. J. Clin. Invest. 90: 1713-1717, 1992. [PubMed: 1430200] [Full Text: https://doi.org/10.1172/JCI116044]
Fairbanks, G., Steck, T. L., Wallach, D. F. H. Electrophoretic analysis of the major polypeptides of the human erythrocyte membrane. Biochemistry 10: 2606-2617, 1971. [PubMed: 4326772] [Full Text: https://doi.org/10.1021/bi00789a030]
Feo, C. J., Fischer, S., Piau, J. P., Grange, M. J., Tchernia, G. Premiere observation de l'absence d'une proteine de la membrane erythrocytaire (bande 4-1) dans un cas d'anemie elliptocytaire familiale. Nouv. Rev. Franc. Hemat. 22: 315-325, 1980. [PubMed: 7255153]
Garbarz, M., Devaux, I., Bournier, O., Grandchamp, B., Dhermy, D. Protein 4.1 Lille, a novel mutation in the downstream initiation codon of protein 4.1 gene associated with heterozygous 4,1(-) hereditary elliptocytosis. Hum. Mutat. 5: 339-340, 1995. [PubMed: 7627190] [Full Text: https://doi.org/10.1002/humu.1380050412]
Kan, Y.-W. Personal Communication. San Francisco, Calif. 2/28/1986.
Lambert, S., Conboy, J., Zail, S. A molecular study of heterozygous protein 4.1 deficiency in hereditary elliptocytosis. Blood 72: 1926-1929, 1988. [PubMed: 3058231]
Marchesi, S. L., Conboy, J., Agre, P., Letsinger, J. T., Marchesi, V. T., Speicher, D. W., Mohandas, N. Molecular analysis of insertion/deletion mutations in protein 4.1 in elliptocytosis. I. Biochemical identification of rearrangements in the spectrin/actin binding domain and functional characterizations. J. Clin. Invest. 86: 516-523, 1990. [PubMed: 2384597] [Full Text: https://doi.org/10.1172/JCI114738]
McGuire, M., Smith, B. L., Agre, P. Distinct variants of erythrocyte protein 4.1 inherited in linkage with elliptocytosis and Rh type in three white families. Blood 72: 287-293, 1988. [PubMed: 3134067]
Parra, M., Gascard, P., Walensky, L. D., Snyder, S. H., Mohandas, N., Conboy, J. G. Cloning and characterization of 4.1G (EPB41L2), a new member of the skeletal protein 4.1 (EPB41) gene family. Genomics 49: 298-306, 1998. [PubMed: 9598318] [Full Text: https://doi.org/10.1006/geno.1998.5265]
Ponthier, J. L., Schluepen, C., Chen, W., Lersch, R. A., Gee, S. L., Hou, V. C., Lo, A. J., Short, S. A., Chasis, J. A., Winkelmann, J. C., Conboy, J. G. Fox-2 splicing factor binds to a conserved intron motif to promote inclusion of protein 4.1R alternative exon 16. J. Biol. Chem. 281: 12468-12474, 2006. [PubMed: 16537540] [Full Text: https://doi.org/10.1074/jbc.M511556200]
Salomao, M., Chen, K., Villalobos, J., Mohandas, N., An, X., Chasis, J. A. Hereditary spherocytosis and hereditary elliptocytosis: aberrant protein sorting during erythroblast enucleation. Blood 116: 267-269, 2010. [PubMed: 20339087] [Full Text: https://doi.org/10.1182/blood-2010-02-264127]
Shi, Z.-T., Afzal, V., Coller, B., Patel, D., Chasis, J. A., Parra, M., Lee, G., Paszty, C., Stevens, M., Walensky, L., Peters, L. L., Mohandas, N., Rubin, E., Conboy, J. G. Protein 4.1R-deficient mice are viable but have erythroid membrane skeleton abnormalities. J. Clin. Invest. 103: 331-340, 1999. [PubMed: 9927493] [Full Text: https://doi.org/10.1172/JCI3858]
Takakuwa, Y., Tchernia, G., Rossi, M., Benabadji, M., Mohandas, N. Restoration of normal membrane stability to unstable protein 4.1-deficient erythrocyte membranes by incorporation of purified protein 4.1. J. Clin. Invest. 78: 80-85, 1986. [PubMed: 3722387] [Full Text: https://doi.org/10.1172/JCI112577]
Tan, J. S., Mohandas, N., Conboy, J. G. Evolutionarily conserved coupling of transcription and alternative splicing in the EPB41 (protein 4.1R) and EPB41L3 (protein 4.1B) genes. Genomics 86: 701-707, 2005. [PubMed: 16242908] [Full Text: https://doi.org/10.1016/j.ygeno.2005.08.005]
Tang, C.-J. C., Tang, T. K. Rapid localization of membrane skeletal protein 4.1 (EL1) to human chromosome 1p33-p34.2 by nonradioactive in situ hybridization. Cytogenet. Cell Genet. 57: 119, 1991. [PubMed: 1914519] [Full Text: https://doi.org/10.1159/000133128]
Tang, T. K., Leto, T. L., Correas, I., Alonso, M. A., Marchesi, V. T., Benz, E. J., Jr. Selective expression of an erythroid-specific isoform of protein 4.1. Proc. Nat. Acad. Sci. 85: 3713-3717, 1988. [PubMed: 3375238] [Full Text: https://doi.org/10.1073/pnas.85.11.3713]
Tchernia, G., Mohandas, N., Shohet, S. B. Deficiency of skeletal membrane protein band 4.1 in homozygous hereditary elliptocytosis: implications for erythrocyte membrane stability. J. Clin. Invest. 68: 454-460, 1981. [PubMed: 6894932] [Full Text: https://doi.org/10.1172/jci110275]