BACKGROUND: Familial hypobetalipoproteinaemia (FHBL) is a codominant disorder characterised by fatty liver and reduced plasma levels of low-density lipoprotein (LDL) and its protein constituent apolipoprotein B (apoB). FHBL is linked to the APOB gene in some but not all known cases. In a group of 59 patients with FHBL genotyped for APOB gene mutations, we found three novel splice-site mutations: c.904+4A-->G in intron 8, c.3843-2A-->G in intron 24 and c.4217-1G-->T in intron 25. OBJECTIVE: To assess the effects of these mutations on apoB pre-mRNA splicing. METHODS: ApoB mRNA was analysed in the liver of one proband and in cells expressing APOB minigenes harbouring the mutations found in the other probands. RESULTS: In the liver of the c.3843-2A-->G carrier, an apoB mRNA devoid of exon 25 was identified, predicted to encode a truncated peptide of 1260 amino acids. The analysis of minigene transcripts in COS-1 cells showed that the c.904+4A-->G mutation caused the formation of an mRNA devoid of exon 8, predicted to encode a short apoB of 247 amino acids. The minigene harbouring the c.4217-1G-->T mutation in intron 25 generated an mRNA in which exon 25 joined to a partially deleted exon 26, resulting from the activation of an acceptor site in exon 26; this mRNA is predicted to encode a truncated protein of 1380 amino acids. All these truncated apoBs were not secreted as constituents of plasma lipoproteins. CONCLUSION: These findings demonstrate the pathogenic effect of rare splice-site mutations of the APOB gene found in FHBL.
BACKGROUND: Familial hypobetalipoproteinaemia (FHBL) is a codominant disorder characterised by fatty liver and reduced plasma levels of low-density lipoprotein (LDL) and its protein constituent apolipoprotein B (apoB). FHBL is linked to the APOB gene in some but not all known cases. In a group of 59 patients with FHBL genotyped for APOB gene mutations, we found three novel splice-site mutations: c.904+4A-->G in intron 8, c.3843-2A-->G in intron 24 and c.4217-1G-->T in intron 25. OBJECTIVE: To assess the effects of these mutations on apoB pre-mRNA splicing. METHODS: ApoB mRNA was analysed in the liver of one proband and in cells expressing APOB minigenes harbouring the mutations found in the other probands. RESULTS: In the liver of the c.3843-2A-->G carrier, an apoB mRNA devoid of exon 25 was identified, predicted to encode a truncated peptide of 1260 amino acids. The analysis of minigene transcripts in COS-1 cells showed that the c.904+4A-->G mutation caused the formation of an mRNA devoid of exon 8, predicted to encode a short apoB of 247 amino acids. The minigene harbouring the c.4217-1G-->T mutation in intron 25 generated an mRNA in which exon 25 joined to a partially deleted exon 26, resulting from the activation of an acceptor site in exon 26; this mRNA is predicted to encode a truncated protein of 1380 amino acids. All these truncated apoBs were not secreted as constituents of plasma lipoproteins. CONCLUSION: These findings demonstrate the pathogenic effect of rare splice-site mutations of the APOB gene found in FHBL.
Authors: Amanda J Whitfield; P Hugh R Barrett; Ken Robertson; Marek F Havlat; Frank M van Bockxmeer; John R Burnett Journal: Clin Chem Date: 2004-10-28 Impact factor: 8.327
Authors: Pin Yue; Bo Yuan; Daniela S Gerhard; Rosalind J Neuman; William L Isley; William S Harris; Gustav Schonfeld Journal: Hum Mutat Date: 2002-08 Impact factor: 4.878
Authors: John R Burnett; Jing Shan; Brooke A Miskie; Amanda J Whitfield; Jane Yuan; Khai Tran; C James McKnight; Robert A Hegele; Zemin Yao Journal: J Biol Chem Date: 2003-01-27 Impact factor: 5.157
Authors: P Tarugi; A Lonardo; C Gabelli; F Sala; G Ballarini; I Cortella; L Previato; S Bertolini; R Cordera; S Calandra Journal: J Lipid Res Date: 2001-10 Impact factor: 5.922
Authors: Johan Björkegren; Anne Beigneux; Martin O Bergo; Jacquelyn J Maher; Stephen G Young Journal: J Biol Chem Date: 2001-12-05 Impact factor: 5.486