- Email: [email protected]
A family with permanent neonatal diabetes due to a novel mutation in INS gene
diabetes research and clinical practice 108 (2015) e28–e30
Contents available at ScienceDirect
Diabetes Research and Clinical Practice jou rnal hom ep ag e: w ww.e l s e v i er . c om/ loca te / d i ab r es
A family with permanent neonatal diabetes due to a novel mutation in INS gene Rumyana Dimova a,*, Tsvetalina Tankova a, Ivelina Gergelcheva b, Ivailo Tournev b, Maya Konstantinova c a
Department of Diabetology, Clinical Center of Endocrinology, Medical University Sofia, 2, Zdrave str., Sofia 1431, Bulgaria b Department of Neurology, Medical University Sofia, 1, Sv. G. Sofiiski str., Sofia 1431, Bulgaria c Paediatric Hospital, Medical University Sofia, 11, Akad. Ivan Geshov boul., Sofia 1431, Bulgaria
article info
abstract
Article history:
In this report we present a family with permanent neonatal diabetes, heterozygous for a
Received 12 January 2015
novel INS gene missense mutation, p.A24V, manifested with marked hyperglycemia and
Accepted 19 February 2015
ketoacidosis, unstable glycemic control, requiring insulin therapy, rapid progression of
Available online 25 February 2015
long-term complications and accompanying physical pathological signs and brain lesions. # 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Heterozyguos INS gene mutation Permanent neonatal diabetes
1.
Introduction
Neonatal diabetes mellitus, either permanent (PNDM) or transient, is a rare monogenic disease related to defects mostly in KCNJ11, ABCC8 or INS genes [1] with an incidence ranging from 1:260,000 [2] to 1:210,000 [3] live births. INS gene mutations have been identified independently by Støy et al. [4] and Colombo et al. [5]. The notion of proteotoxicity has been assumed as the underlying pathogenic mechanism causing beta-cell dysfunction [6,7].
2.
Case report
The proband is a 23-year-old male of non-consanguineous parents, with Bulgarian ancestry, diagnosed with diabetes at 6 months of age, with a strong family history of early-onset diabetes (Fig. 1). The affected relatives are his father, uncle and aunt, diagnosed with diabetes at 2 years, 1 year and 6 months,
and 2 years of age, respectively, and, in addition, his grandmother diagnosed with type 2 diabetes and obesity died at the age of 67 from stroke. All affected family-members have presented with markedly high plasma glucose levels and ketoacidosis at diagnosis, on an intensive insulin regimen since the onset of the disease, maintaining long-term poor glycemic control, HbA1c >7.5% (58 mmol/mol). Father died at the age of 40, with overt peripheral neuropathy, nephropathy with end-stage chronic kidney disease (CKD) on hemodialysis, and macroangiopathy with a history of 2 strokes. Currently, the index subject and both siblings, a 48-year-old male and a 43-year-old female, have presented with relatively short stature (about 162 cm), a slight limitation of vertical, version eye movements upwards and mongoloid-like facies. The proband was diagnosed with subclinical sensorimotor polyneuropathy and non-proliferative retinopathy. Liver, kidney and thyroid function, mental and motor development have been normal. Both siblings have presented with advanced chronic complications—severe demyelinating polyneuropathy; proliferative retinopathy, treated with argon laser
* Corresponding author. Tel.: +359 887 212 573. E-mail addresses: [email protected], [email protected] (R. Dimova). http://dx.doi.org/10.1016/j.diabres.2015.02.021 0168-8227/# 2015 Elsevier Ireland Ltd. All rights reserved.
diabetes research and clinical practice 108 (2015) e28–e30
Fig. 1 – The family pedigree. The proband is indicated by the arrow. All affected relatives are pointed out by black shaded boxes, all deceased people are designated by a slash and the grandmother with type 2 diabetes is marked by a yellow shaded box. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
photocoagulation, and cataract; nephropathy with CKD stage IIIa and I; and macroangiopathy, peripheral artery disease and ischemic heart disease, respectively; and arterial hypertension. Additionally, the aunt has been diagnosed with breast cancer at the age of 42, has prosthesis due to congenital microphthalmia and 2 miscarriages. Their laboratory tests have revealed negative GAD65 and IA2 antibodies and undetectable serum C-peptide. Both siblings brain magnetic resonance imaging has demonstrated ovoid hyper-intense lesions on T2 and FLAIR images, located in the periventricular white matter in the frontal lobes and dilated perivascular spaces.
3.
Results
Blood samples from the proband, his uncle and aunt were taken after obtaining informed consent. Mutation analysis of all coding regions and exon/intron boundaries of the KCNJ11, ABCC8, INS and EIF2AK3 genes (NM_000525.3, U63421 and L78208, NM_000207.2 and AF110146.1), by Sanger sequencing was undertaken in the index patient. Sequencing analysis has shown that the proband is heterozygous for a novel INS missense mutation, p.A24V (c.71C > T). The alanine residue in exon 2, codon 24 is highly conserved across species and a different mutation at the same residue (p.A24D) has been reported in a patient diagnosed with diabetes at the age of 9 weeks [4]. It is therefore likely that the p.A24V mutation is pathogenic, encoding signal peptide. This result confirms a diagnosis of PNDM due to a mutation in INS gene with autosomal dominant inheritance [4]. The affected siblings INS gene testing has identified p.A24V mutation as well, and confirmed its pathogenicity. The p.A24V substitution has not been identified in over 1000 patients referred to Exeter Molecular Genetics Laboratory for genetic testing for neonatal diabetes.
e29
been found to be caused by mutations in KCNJ11 gene in 31% of cases, INS gene in 12%, GCK gene in 4%, EIF2AK3 gene in 3%, and FOXP3 gene in 1.4%, although the affected genes in 39% of cases are still unclarified [9]. The onset of PNDM in the reported family varies between 6 months and 2 years following birth. In previously detected A24D mutation carriers the onset of NDM ranges from 4 weeks to 7 years [9], A23S mutation results in non-autoimmune type 1 diabetes with onset at 6 years of age, and R6C or H mutation is characterized by MODY, starting at 15–65 years of age [10]. Heterozygous INS mutations account for 12–20% of PNDM with onset before 6 months of age [3,9,11] and might be more frequent [9] or less than 2% [11] in the range between 6 and 12 months of age as a cause of infancy-onset diabetes, nonautoimmune type 1 diabetes and MODY [4,8,9,12]. Therefore, screening should be performed in all diabetic patients diagnosed before 1 year of age, with MODY and selected cases of type 1 diabetes phenotypes [12]. Regarding the original report, PNDM generally manifests during the first 6 months of life with marked hyperglycemia, ketoacidosis and insulin deficiency, requiring lifelong insulin treatment, which is confirmed in our case [4,5]. All carriers show advanced chronic diabetic complications. Both siblings have presented with proliferative retinopathy in contrast to Iafusco et al., reporting no proliferative retinopathy in 15 PNDM patients with median duration of 24 years [13]. All authors have reported isolated diabetes in heterozygous INS mutation carriers [3,8]. Therefore, the syndromic clinical features of the reported family, associated with some physical pathological signs—skeletal and eye movement abnormalities, and brain lesions, probably due to a demyelinating process, strongly point towards some additional unknown genetic defect(s). Presumably the mechanism of disease is similar to those of previously described A24D mutation. It causes misfolding and defective trafficking of proinsulin, exerting dominant-negative effect on insulin production and b-cell apoptosis [4,5,10,14]. Although INS gene differs between humans and rodents, INS2 missense mutations in Akita and Munich mice models result in proteotoxic disruption of interchain disulphide bond formation [6,7,15].
Conclusion Heterozygous INS mutations lead to PNDM and should be taken into consideration in neonatal and early-infancy periods.
Conflict of interest statement The authors declare that they have no conflict of interest.
Acknowledgments 4.
Discussion
The INS mutation occurs in 10% of all PNDM cases [8]. In a large cohort PNDM, diagnosed within 6 months following birth, has
We are grateful to all family members participating in the study. Genetic testing was provided by the University of Exeter Medical School Genetics Laboratory with funding from the
e30
diabetes research and clinical practice 108 (2015) e28–e30
Wellcome Trust to Professors Andrew Hattersley and Sian Ellard (testing is available free of charge for any patient diagnosed with diabetes before the age of 9 months see www.diabetesgenes.org). [9]
references
[1] Hattersley A, Bruining J, Shield J, Njolstad P, Donaghue KC. The diagnosis and management of monogenic diabetes in children and adolescents. Pediatr Diabetes 2009;10(Suppl. 12):33–42. [2] Slingerland AS, Shields BM, Flanagan SE, Bruining GJ, Noordam K, Gach A, et al. Referral rates for diagnostic testing support an incidence of permanent neonatal diabetes in three European countries of at least 1 in 260,000 live births. Diabetologia 2009;52:1683–5. [3] Russo L, Iafusco D, Brescianini S, Nocerino V, Bizzarri C, Toni S, et al., ISPED Early Diabetes Study Group. Permanent diabetes during the first year of life: multiple gene screening in 54 patients. Diabetologia 2011;54:1693–701. [4] Støy J, Edghill EL, Flanagan SE, Ye H, Paz VP, Pluzhnikov A, et al., Neonatal Diabetes International Collaborative Group. Insulin gene mutations as a cause of permanent neonatal diabetes. Proc Natl Acad Sci USA 2007;104:15040–4. [5] Colombo C, Porzio O, Liu M, Massa O, Vasta M, Salardi S, et al., Early Onset Diabetes Study Group of the Italian Society of Pediatric Endocrinology and Diabetes (SIEDP). Seven mutations in the human insulin gene linked to permanent neonatal/infancy-onset diabetes mellitus. J Clin Invest 2008;118:2148–56. [6] Ron D. Proteotoxicity in the endoplasmic reticulum: lessons from the Akita diabetic mouse. J Clin Invest 2002;109:443–5. [7] Herbach N, Rathkolb B, Kemter E, Pichl L, Klaften M, de Angelis MH, et al. Dominant-negative effects of a novel mutated Ins2 allele causes early-onset diabetes and severe beta-cell loss in Munich Ins2C95S mutant mice. Diabetes 2007;56:1268–76. [8] Polak M, Dechaume A, Cave H, Nimri R, Crosnier H, Sulmont V, et al., French ND (Neonatal Diabetes) Study
[10]
[11]
[12]
[13]
[14]
[15]
Group. Heterozygous missense mutations in the insulin gene are linked to permanent diabetes appearing in the neonatal period or in early infancy: a report from the French ND (Neonatal Diabetes) Study Group. Diabetes 2008;57:1115–9. Edghill EL, Flanagan SE, Patch AM, Boustred C, Parrish A, Shields B, et al., the Neonatal Diabetes International Collaborative Group. Insulin mutation screening in 1044 patients with diabetes: mutations in the INS gene are a common cause of neonatal diabetes but a rare cause of diabetes diagnosed in childhood or adulthood. Diabetes 2008;57:1034–42. Liu M, Hodish I, Haataja L, Lara-Lemus R, Rajpal G, Wright J, et al. Proinsulin misfolding and diabetes: mutant INS geneinduced diabetes of youth. Trends Endocrinol Metab 2010;21:652–9. Støy J, Steiner DF, Park SY, Ye H, Philipson LH, Bell GI. Clinical and molecular genetics of neonatal diabetes due to mutations in the insulin gene. Rev Endocr Metab Disord 2010;11:205–15. Molven A, Ringdal M, Nordbø AM, Raeder H, Støy J, Lipkind GM, et al., Norwegian Childhood Diabetes Study Group. Mutations in the insulin gene can cause MODY and autoantibody-negative type 1 diabetes. Diabetes 2008;57:1131–5. Iafusco D, Salardi S, Chiari G, Toni S, Rabbone I, Pesavento R, et al., Early Onset Diabetes Study Group of the Italian Society of Pediatric Endocrinology and Diabetology (ISPED). No sign of proliferative retinopathy in 15 patients with permanent neonatal diabetes with a median diabetes duration of 24 years. Diabetes Care 2014;37:181–2. Meur G, Simon A, Harun N, Virally M, Dechaume A, Bonnefond A, et al. Insulin gene mutations resulting in early-onset diabetes: marked differences in clinical presentation, metabolic status, and pathogenic effect through endoplasmic reticulum retention. Diabetes 2010; 59:653–61. Flanagan SE, Franco ED, Allen HL, Zerah M, Abdul-Rasoul MM, Edge JA, et al. Analysis of transcription factors key for mouse pancreatic development establishes NKX2-2 and MNX1 mutations as causes of neonatal diabetes in man. Cell Metab 2014;19:146–54.
Contents available at ScienceDirect
Diabetes Research and Clinical Practice jou rnal hom ep ag e: w ww.e l s e v i er . c om/ loca te / d i ab r es
A family with permanent neonatal diabetes due to a novel mutation in INS gene Rumyana Dimova a,*, Tsvetalina Tankova a, Ivelina Gergelcheva b, Ivailo Tournev b, Maya Konstantinova c a
Department of Diabetology, Clinical Center of Endocrinology, Medical University Sofia, 2, Zdrave str., Sofia 1431, Bulgaria b Department of Neurology, Medical University Sofia, 1, Sv. G. Sofiiski str., Sofia 1431, Bulgaria c Paediatric Hospital, Medical University Sofia, 11, Akad. Ivan Geshov boul., Sofia 1431, Bulgaria
article info
abstract
Article history:
In this report we present a family with permanent neonatal diabetes, heterozygous for a
Received 12 January 2015
novel INS gene missense mutation, p.A24V, manifested with marked hyperglycemia and
Accepted 19 February 2015
ketoacidosis, unstable glycemic control, requiring insulin therapy, rapid progression of
Available online 25 February 2015
long-term complications and accompanying physical pathological signs and brain lesions. # 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Heterozyguos INS gene mutation Permanent neonatal diabetes
1.
Introduction
Neonatal diabetes mellitus, either permanent (PNDM) or transient, is a rare monogenic disease related to defects mostly in KCNJ11, ABCC8 or INS genes [1] with an incidence ranging from 1:260,000 [2] to 1:210,000 [3] live births. INS gene mutations have been identified independently by Støy et al. [4] and Colombo et al. [5]. The notion of proteotoxicity has been assumed as the underlying pathogenic mechanism causing beta-cell dysfunction [6,7].
2.
Case report
The proband is a 23-year-old male of non-consanguineous parents, with Bulgarian ancestry, diagnosed with diabetes at 6 months of age, with a strong family history of early-onset diabetes (Fig. 1). The affected relatives are his father, uncle and aunt, diagnosed with diabetes at 2 years, 1 year and 6 months,
and 2 years of age, respectively, and, in addition, his grandmother diagnosed with type 2 diabetes and obesity died at the age of 67 from stroke. All affected family-members have presented with markedly high plasma glucose levels and ketoacidosis at diagnosis, on an intensive insulin regimen since the onset of the disease, maintaining long-term poor glycemic control, HbA1c >7.5% (58 mmol/mol). Father died at the age of 40, with overt peripheral neuropathy, nephropathy with end-stage chronic kidney disease (CKD) on hemodialysis, and macroangiopathy with a history of 2 strokes. Currently, the index subject and both siblings, a 48-year-old male and a 43-year-old female, have presented with relatively short stature (about 162 cm), a slight limitation of vertical, version eye movements upwards and mongoloid-like facies. The proband was diagnosed with subclinical sensorimotor polyneuropathy and non-proliferative retinopathy. Liver, kidney and thyroid function, mental and motor development have been normal. Both siblings have presented with advanced chronic complications—severe demyelinating polyneuropathy; proliferative retinopathy, treated with argon laser
* Corresponding author. Tel.: +359 887 212 573. E-mail addresses: [email protected], [email protected] (R. Dimova). http://dx.doi.org/10.1016/j.diabres.2015.02.021 0168-8227/# 2015 Elsevier Ireland Ltd. All rights reserved.
diabetes research and clinical practice 108 (2015) e28–e30
Fig. 1 – The family pedigree. The proband is indicated by the arrow. All affected relatives are pointed out by black shaded boxes, all deceased people are designated by a slash and the grandmother with type 2 diabetes is marked by a yellow shaded box. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
photocoagulation, and cataract; nephropathy with CKD stage IIIa and I; and macroangiopathy, peripheral artery disease and ischemic heart disease, respectively; and arterial hypertension. Additionally, the aunt has been diagnosed with breast cancer at the age of 42, has prosthesis due to congenital microphthalmia and 2 miscarriages. Their laboratory tests have revealed negative GAD65 and IA2 antibodies and undetectable serum C-peptide. Both siblings brain magnetic resonance imaging has demonstrated ovoid hyper-intense lesions on T2 and FLAIR images, located in the periventricular white matter in the frontal lobes and dilated perivascular spaces.
3.
Results
Blood samples from the proband, his uncle and aunt were taken after obtaining informed consent. Mutation analysis of all coding regions and exon/intron boundaries of the KCNJ11, ABCC8, INS and EIF2AK3 genes (NM_000525.3, U63421 and L78208, NM_000207.2 and AF110146.1), by Sanger sequencing was undertaken in the index patient. Sequencing analysis has shown that the proband is heterozygous for a novel INS missense mutation, p.A24V (c.71C > T). The alanine residue in exon 2, codon 24 is highly conserved across species and a different mutation at the same residue (p.A24D) has been reported in a patient diagnosed with diabetes at the age of 9 weeks [4]. It is therefore likely that the p.A24V mutation is pathogenic, encoding signal peptide. This result confirms a diagnosis of PNDM due to a mutation in INS gene with autosomal dominant inheritance [4]. The affected siblings INS gene testing has identified p.A24V mutation as well, and confirmed its pathogenicity. The p.A24V substitution has not been identified in over 1000 patients referred to Exeter Molecular Genetics Laboratory for genetic testing for neonatal diabetes.
e29
been found to be caused by mutations in KCNJ11 gene in 31% of cases, INS gene in 12%, GCK gene in 4%, EIF2AK3 gene in 3%, and FOXP3 gene in 1.4%, although the affected genes in 39% of cases are still unclarified [9]. The onset of PNDM in the reported family varies between 6 months and 2 years following birth. In previously detected A24D mutation carriers the onset of NDM ranges from 4 weeks to 7 years [9], A23S mutation results in non-autoimmune type 1 diabetes with onset at 6 years of age, and R6C or H mutation is characterized by MODY, starting at 15–65 years of age [10]. Heterozygous INS mutations account for 12–20% of PNDM with onset before 6 months of age [3,9,11] and might be more frequent [9] or less than 2% [11] in the range between 6 and 12 months of age as a cause of infancy-onset diabetes, nonautoimmune type 1 diabetes and MODY [4,8,9,12]. Therefore, screening should be performed in all diabetic patients diagnosed before 1 year of age, with MODY and selected cases of type 1 diabetes phenotypes [12]. Regarding the original report, PNDM generally manifests during the first 6 months of life with marked hyperglycemia, ketoacidosis and insulin deficiency, requiring lifelong insulin treatment, which is confirmed in our case [4,5]. All carriers show advanced chronic diabetic complications. Both siblings have presented with proliferative retinopathy in contrast to Iafusco et al., reporting no proliferative retinopathy in 15 PNDM patients with median duration of 24 years [13]. All authors have reported isolated diabetes in heterozygous INS mutation carriers [3,8]. Therefore, the syndromic clinical features of the reported family, associated with some physical pathological signs—skeletal and eye movement abnormalities, and brain lesions, probably due to a demyelinating process, strongly point towards some additional unknown genetic defect(s). Presumably the mechanism of disease is similar to those of previously described A24D mutation. It causes misfolding and defective trafficking of proinsulin, exerting dominant-negative effect on insulin production and b-cell apoptosis [4,5,10,14]. Although INS gene differs between humans and rodents, INS2 missense mutations in Akita and Munich mice models result in proteotoxic disruption of interchain disulphide bond formation [6,7,15].
Conclusion Heterozygous INS mutations lead to PNDM and should be taken into consideration in neonatal and early-infancy periods.
Conflict of interest statement The authors declare that they have no conflict of interest.
Acknowledgments 4.
Discussion
The INS mutation occurs in 10% of all PNDM cases [8]. In a large cohort PNDM, diagnosed within 6 months following birth, has
We are grateful to all family members participating in the study. Genetic testing was provided by the University of Exeter Medical School Genetics Laboratory with funding from the
e30
diabetes research and clinical practice 108 (2015) e28–e30
Wellcome Trust to Professors Andrew Hattersley and Sian Ellard (testing is available free of charge for any patient diagnosed with diabetes before the age of 9 months see www.diabetesgenes.org). [9]
references
[1] Hattersley A, Bruining J, Shield J, Njolstad P, Donaghue KC. The diagnosis and management of monogenic diabetes in children and adolescents. Pediatr Diabetes 2009;10(Suppl. 12):33–42. [2] Slingerland AS, Shields BM, Flanagan SE, Bruining GJ, Noordam K, Gach A, et al. Referral rates for diagnostic testing support an incidence of permanent neonatal diabetes in three European countries of at least 1 in 260,000 live births. Diabetologia 2009;52:1683–5. [3] Russo L, Iafusco D, Brescianini S, Nocerino V, Bizzarri C, Toni S, et al., ISPED Early Diabetes Study Group. Permanent diabetes during the first year of life: multiple gene screening in 54 patients. Diabetologia 2011;54:1693–701. [4] Støy J, Edghill EL, Flanagan SE, Ye H, Paz VP, Pluzhnikov A, et al., Neonatal Diabetes International Collaborative Group. Insulin gene mutations as a cause of permanent neonatal diabetes. Proc Natl Acad Sci USA 2007;104:15040–4. [5] Colombo C, Porzio O, Liu M, Massa O, Vasta M, Salardi S, et al., Early Onset Diabetes Study Group of the Italian Society of Pediatric Endocrinology and Diabetes (SIEDP). Seven mutations in the human insulin gene linked to permanent neonatal/infancy-onset diabetes mellitus. J Clin Invest 2008;118:2148–56. [6] Ron D. Proteotoxicity in the endoplasmic reticulum: lessons from the Akita diabetic mouse. J Clin Invest 2002;109:443–5. [7] Herbach N, Rathkolb B, Kemter E, Pichl L, Klaften M, de Angelis MH, et al. Dominant-negative effects of a novel mutated Ins2 allele causes early-onset diabetes and severe beta-cell loss in Munich Ins2C95S mutant mice. Diabetes 2007;56:1268–76. [8] Polak M, Dechaume A, Cave H, Nimri R, Crosnier H, Sulmont V, et al., French ND (Neonatal Diabetes) Study
[10]
[11]
[12]
[13]
[14]
[15]
Group. Heterozygous missense mutations in the insulin gene are linked to permanent diabetes appearing in the neonatal period or in early infancy: a report from the French ND (Neonatal Diabetes) Study Group. Diabetes 2008;57:1115–9. Edghill EL, Flanagan SE, Patch AM, Boustred C, Parrish A, Shields B, et al., the Neonatal Diabetes International Collaborative Group. Insulin mutation screening in 1044 patients with diabetes: mutations in the INS gene are a common cause of neonatal diabetes but a rare cause of diabetes diagnosed in childhood or adulthood. Diabetes 2008;57:1034–42. Liu M, Hodish I, Haataja L, Lara-Lemus R, Rajpal G, Wright J, et al. Proinsulin misfolding and diabetes: mutant INS geneinduced diabetes of youth. Trends Endocrinol Metab 2010;21:652–9. Støy J, Steiner DF, Park SY, Ye H, Philipson LH, Bell GI. Clinical and molecular genetics of neonatal diabetes due to mutations in the insulin gene. Rev Endocr Metab Disord 2010;11:205–15. Molven A, Ringdal M, Nordbø AM, Raeder H, Støy J, Lipkind GM, et al., Norwegian Childhood Diabetes Study Group. Mutations in the insulin gene can cause MODY and autoantibody-negative type 1 diabetes. Diabetes 2008;57:1131–5. Iafusco D, Salardi S, Chiari G, Toni S, Rabbone I, Pesavento R, et al., Early Onset Diabetes Study Group of the Italian Society of Pediatric Endocrinology and Diabetology (ISPED). No sign of proliferative retinopathy in 15 patients with permanent neonatal diabetes with a median diabetes duration of 24 years. Diabetes Care 2014;37:181–2. Meur G, Simon A, Harun N, Virally M, Dechaume A, Bonnefond A, et al. Insulin gene mutations resulting in early-onset diabetes: marked differences in clinical presentation, metabolic status, and pathogenic effect through endoplasmic reticulum retention. Diabetes 2010; 59:653–61. Flanagan SE, Franco ED, Allen HL, Zerah M, Abdul-Rasoul MM, Edge JA, et al. Analysis of transcription factors key for mouse pancreatic development establishes NKX2-2 and MNX1 mutations as causes of neonatal diabetes in man. Cell Metab 2014;19:146–54.