ABCMdb

PMID: 10334322

Otonkoski T, Ammala C, Huopio H, Cote GJ, Chapman J, Cosgrove K, Ashfield R, Huang E, Komulainen J, Ashcroft FM, Dunne MJ, Kere J, Thomas PM
A point mutation inactivating the sulfonylurea receptor causes the severe form of persistent hyperinsulinemic hypoglycemia of infancy in Finland.
Diabetes. 1999 Feb;48(2):408-15., [PubMed]

Sentences

No. Mutations Sentence Comment

4 ABCC8 p.Val187Asp ABCC8 p.Val187Asp Sequence analysis revealed a novel point mutation in exon 4 of SUR1, predicting a valine to aspartic acid change at amino acid 187 (V187D). Login to comment 5 ABCC8 p.Val187Asp Of the total cases, 15 affected individuals harbored this mutation in heterozygous or homozygous form, and all of these had severe hyperinsulinemia that responded poorly to medical treatment and required subtotal pancreatectomy. No KATP channel activity was observed in -cells isolated from a homozygous patient or after coexpression of recombinant Kir6.2 and SUR1 carrying the V187D mutation. Login to comment 57 ABCC8 p.Val187Asp To detect the V187D mutation, PCR amplification of genomic DNA was performed using the primers 5 -GTGAGTGTACACATGATG and 5 -CAGAGCCA GAGCCTCTGCTT. Login to comment 85 ABCC8 p.Val187Asp Oocytes were then co-injected with a mixture of mRNAs encoding Kir6.2 (~0.04 ng) and either wild-type SUR1 or V187D SUR1 (~2 ng) at dilutions yielding a final injection volume of about ~50 nl/oocyte. Login to comment 89 ABCC8 p.Val187Asp Open circles represent carriers of the V187D mutation of SUR1, detected with the Tth111I restriction endonuclease test. Login to comment 123 ABCC8 p.Val187Asp Even in this TABLE 1 Major clinical findings in Finnish PHHI patients Gestational Birth weight Blood glucose (mmol/l); Age at Mutation Patient Sex age (weeks) (g) plasma insulin (pmol/l) pancreatectomy (days) V187D 1 M 34 3,920 (+4.6) 0.5; 534 23 +/- 2 M 33 2,350 (+0.2) 5.0; 282 29 - 3 F 35 3,120 (+1.1) 5.0; 342 22 +/- 4 M 36 3,940 (+2.4) 3.0; 564 16 +/+ 5 M 39 5,080 (+3.3) 1.8; 96 57 +/- 6 M 39 3,970 (+0.9) 1.2; 78 - - 7 F 37 3,420 (+0.7) 1.4; 236 38 +/- 8 F 39 4,020 (+1.3) 1.5; 341 161 +/- 9 F 29 2,070 (+4.6) 2.2; 440 31 +/+ 10 M 40 3,710 (0.0) 1.5; 190 38 +/- 11 F 39 3,900 (+1.1) 1.6; 654 11 +/- 12 F 33 3,710 (+5.0) 1.4; 1040 12 +/+ 13 F 37 4,100 (+2.4) 1.7; 149 59 +/+ 14 F 34 3,700 (+4.0) 2.2; 396 - - 15 M 39 3,845 (+0.7) 2.2; 1200 11 +/- 16 M 36 3,150 (+0.4) 1.2; 186 - - 17 M 36 5,250 (+5.6) 2.2; 874 21/196 +/+ 18 M 35 2,910 (+0.3) 2.8; 215 82 +/- 19 M 35 4,565 (+5.2) 4.1; 850 11 - 20 F 38 4,330 (+0.6) 1.5; 138 - - 21 M 28 1,770 (+3.8) 1.8; 615 15 (+/+)* 22 M 39 2,900 (-1.5) 2.1; 294 - - 23 F 37 5,360 (+5.7) 2.4; 984 - - 24 F 37 4,490 (+3.3) 1.2; 257 - - Data are n or n (SD). Login to comment 136 ABCC8 p.Val187Asp The geographicaldistribution of birthplaces for parents carrying the marker haplotype and V187D supports a single origin for the mutation (Fig. 1). Login to comment 141 ABCC8 p.Gly716Val The SUR1 gene mutations 1672-20A→G (intron 11), G716V, 2292-1G→A (intron 18), 3992-9G→A (intron 32), G1400D(23)X, 1388 and G1479R, and the Kir6.2 gene mutation L147P, were not present when assayed for by restriction digestion of PCR products amplified from genomic DNA samples as previously described (8,9,11,14). Login to comment 144 ABCC8 p.Val187Asp This point mutation is predicted to substitute a valine for an aspartic acid residue at site 187 of the SUR1 protein (V187D). Login to comment 150 ABCC8 p.Val187Asp An additional 20 Finnish PHHI families were analyzed for the presence of the V187D mutation. Login to comment 153 ABCC8 p.Val187Asp Presence of the V187D mutation was associated with a severeclinical phenotype. Login to comment 155 ABCC8 p.Val187Asp None of the 23 additional individuals who came from outside Finland, were of diverse ethnic origin, and were affected with classic PHHI possessed the V187D mutation as assessed by the Tth111I restriction assay. Login to comment 156 ABCC8 p.Val187Asp This demonstrated that the V187D mutation is rare in the PHHI population at large and that its prevalence within the Finnish population may be attributed to a founder effect. Login to comment 160 ABCC8 p.Val187Asp ABCC8 p.Val187Asp ABCC8 p.Val187Asp of control Haplotype with V187D without V187D chromosomes 2-10-5-7-8-8 13 0 0 3-10-5-7-8-8 1 0 1 2-10-5-7-8-7 1 0 0 2-10-5-7-10-7 1 0 0 2-10-5-7-2-9 1 0 0 2-10-5-7-10-10 1 0 0 All other haplotypes 0 20 32 Total 18 24 33 The PHHI-associated chromosomes were divided in two groups based on the occurrence of the V187D mutation. Login to comment 161 ABCC8 p.Val187Asp All haplotypes associated with V187D were considered derivatives of a single ancestral chromosome with historical recombinations. Login to comment 166 ABCC8 p.Val187Asp We therefore screened 100 chromosomes from normal individuals living in this area and found the V187D mutation in heterozygous form in one of them. Login to comment 168 ABCC8 p.Val187Asp These results are consistent with the idea that V187D is not a common polymorphism. Login to comment 170 ABCC8 p.Val187Asp The functional properties of KATP channels in -cells isolated from a PHHI patient homozygous for the V187D mutation (case 4) were studied using both intact cell recordings and cell-free inside-out patches. Login to comment 180 ABCC8 p.Val187Asp The relationship between the novel SUR1 gene defect and loss of channel function was therefore investigated in recombinant experiments with SUR1 containing the V187D mutation identified in our PHHI patients. Login to comment 182 ABCC8 p.Val187Asp Whole-cell currents were recorded from Xenopus oocytes injected with mRNA encoding Kir6.2 and with either wild-type SUR1 (wt-SUR1) or SUR1 engineered to carry the mutation found in the Finnish population of PHHI patients (SUR1-V187D). Login to comment 183 ABCC8 p.Val187Asp Under basal conditions, currents recorded from oocytes injected with Kir6.2/wt-SUR1 (n = 5) or Kir6.2/SUR1-V187D (n = 5) were no different from those measured in oocytes injected with water (n = 4), entirely consistent with previous observations (24). Login to comment 185 ABCC8 p.Val187Asp No such increase in current was observed in response to sodium azide in either control oocytes or oocytes injectedwith Kir6.2/SUR1-V187D (Fig. 4A and B). Login to comment 186 ABCC8 p.Val187Asp This lack of response observed in Kir6.2/SUR1-V187D-injected oocytes may have arisen because the mutant channel is insensitive to metabolic regulation or because it does not form a functional channel in the plasma membrane. Login to comment 187 ABCC8 p.Val187Asp To determine which of these possibilities is correct, we recordedrecombinant KATP channel activityingiant inside-out membranepatches.Figure4C shows currents elicitedbya voltage-ramp from -100 to +100 mV in the cell-attached condition (c/a) and after excision (i/o) into the ATP-free solution recorded from oocytes injected with wt-SUR1/Kir6.2 or Kir6.2/SUR1-V187D. Login to comment 189 ABCC8 p.Val187Asp By contrast, there was no increase in KATP channel activity (Fig. 4C [right panel] and D) in patches excised fromoocytes injected with Kir6.2/SUR1-V187D. Login to comment 190 ABCC8 p.Val187Asp These findings were consistent with those obtained from acutely isolated PHHI -cells (Fig. 3B) and suggested that the presence of the V187D mutation renders the channel completely nonfunctional. Login to comment 192 ABCC8 p.Val187Asp We have reported here that a single mutation in the SUR1 gene, V187D, detected in 18of42disease-associated chromosomes,revealed FIG. 2. Login to comment 193 ABCC8 p.Val187Asp Demonstration of the V187D mutation. Login to comment 205 ABCC8 p.Val187Asp ABCC8 p.Val187Asp The V187D mutationwas not detected in 9 families, although in 5 of these families, one or both of the disease-associated chromosomes carried partial haplotypes observedin otherpatients heterozygous for V187D. Login to comment 210 ABCC8 p.Val187Asp The in vitro studies described here have demonstrated clearly that the V187D point mutation leads to loss of functional KATP channelexpression, even in excised patches, and thus falls into the former group. Login to comment 212 ABCC8 p.Asn188Ser Interestingly, one of these mutations (N188S) lies adjacent to that reported here, at the cytosolic end of the predicted fifth transmembrane domain (using the topology of Tsnuandy et al. [28]). Login to comment 213 ABCC8 p.Asn188Ser The N188S mutation does not alter the sensitivity of the KATP channel to ATP or Mg-ADP, butappears to reduce the level of functional expression (31). Login to comment 214 ABCC8 p.Asn188Ser ABCC8 p.Val187Asp The V187D mutation appears to be more severe than N188S, as we could not observe any KATP channel activity in excised patches. Login to comment 222 ABCC8 p.Val187Asp In contrast, in Finnish patients the V187D mutation was strongly associated with a severe form of the disease. Login to comment 223 ABCC8 p.Val187Asp It is interesting that the clinical phenotype of PHHI was equally severe, whether the patients were homo- or heterozygous for the V187D mutation. Login to comment 234 ABCC8 p.Val187Asp presence ofeven a single copy of the V187D mutation will prevent the generation of functionally operating KATP channels with high diazoxide sensitivity, if another, possibly less severe mutation is also present. Login to comment 236 ABCC8 p.Val187Asp The presence of the V187D mutation can be easily detected. Login to comment 238 ABCC8 p.Val187Asp Identification of the V187D mutation is prognostically valuable because we observed that this mutation was invariably associated with a severe disease that responded poorly to medication in all cases. Login to comment