Genetics in Paediatrics Diagnostics Aetiology Treatment Prognosis Prediktion Advise Research
Genetic nomenclature,, abbreviations.. Mendels first law: Random transmittance to off-spring of the two chromosomes in a pair Meiosis: : cell division when the gametes are formed Crossing-over over: change of genetic material Recombination: Several cross-over over events between two genes Dominant: One disease allele sufficient (heterozygous) Recessive: Two alleles necessary (homozygous) Genom maps: Physical and genetic Genetic markers: Mini/microsattelite markers; SNPs (Single Nucleotide Polymorphisms= polymorphism on a single base pari) Linkage analyses: Linkage between phenotype and locus Epigenetics
Genetics in Paediatrics 1/40 of all newborns have malformations,, of whom half genetic background 50% of all childhood blindness and deafness genetic cause Genetic factors of importance for all disorders!
Genetics in Paediatrics How does genetics influence your role/work as a doctor??
Family history of importance for.. Allergies Asthma Autoimmune diseases - Celiak disease - Crohn s disease - Hypo/Hyper Hyper thyroidism - Type 1 diabetes - Rheumatoid Arthritis Diabetes type 2 Epilepsia Growth Obesity. Accidents Common cold Headache eg migraine Hernia Infectious sensitivity Pain in the stomach Pylorostenos Urinary Tract problems..
Gene imbalance Autosomal - Trisomi 21; Down s syndrome - Trisomi 18, Edwards syndrome - Trisomi 13, Patau syndrome Sex chromosome imbalance - 45,X: Turner syndrome - 47, XXY, Klinefelters syndrome - Fragile X-syndromeX
Trisomi 21, Down s syndrome 1/700 babies. ( 1/100 when mother >40 years) Hypotonia,, upward sloping palpebral fissures, protruding tongue, single palmar creases, short stature Mild to moderate developmental delay.(iq 25-70). Usually happy and affectionate. 15-20% die <5 years, usually because of VOC. At 40 years all surviving have Alzheimers disease
Turners syndrom (45,X). 1/ 5000 liveborn females.( only 3-5% 3 Turner conceptions survive third trimester). Short stature, neck webbing, puffy hands, low posterior hairline, widely spaced nipples, Amenorre,, infertility VOC
Klinefelters syndrome (47, X,X,Y). 1/1000 males. Infants normal. Intellectual development 10-20 points below unaffected siblings. Taller. Infertile. Additional X-chromosomes X marked hypogonadism and mental retardation
Single gene ( Mendelian) inheritance Autosomal Dominant. >3000 conditions. 1 chance in 2 that the child will inherit the disorder. Vertical transmission. Autosomal recessive. Homozygous needed for disease. Ca 1500 disorders. ¼ of children to an affected parent. Sex-linked ( X-linked) X recessive. 300 disorders known. ½ daughters carriers, and ½ sons affected. Sex-linked dominant
Autosomal Dominant Achondroplasi Familial hypercholesterolemia Hungtintons disease Marfan syndrome Myoton Dystoni MODY Neurofimbromatosis Recklinghausen Osteogenesis imperfecta Polycystic kidney Polyposis coli Spherocytosis Tuberose sclerosis
MODY ( Maturity Onset Diabetes in the Young) MODY 1:Mutationer krom 20. HNF-4 alfa.nedsatt insulinsvar på p glukos. Gradvis insulinberoende MODY 2: Mutationer krom 7. Glukokinas.. Sällan S insulinberoende MODY 3: Mutationer krom 12. HNF-1 1 alfa. Nedsatt insulinsvar pg glukos. Gradvis insulinberoende.- Vanligaste formen. MODY 4: Krom 13. Insulinpromotor faktor-1. MODY 5: Krom 17. HNF-1 1 beta Johnny Ludvigsson
Autosomal recessive. PKU ( Phenylketonuria) alfa1 antitrypsin deficiency Cystic fibrosis Sickle Cell anemia Thalassemia
Sex-linked ( X-linked) X recessive Duchennes muscular dystrophy Brutons agammaglublinemaia Hemophilia A ( Factors VIII deficiency) Christmas disease / Hemophilia B ( Factors IX deficiency) Red-green colour blindness
Genetic imprinting A certain genetic defect may give different expression (disorder) depending on whether the defect is inheretid from the father or mother Environmental factors (during pregnancy) may influence the gene expression of the child
Polygenic inheritance Autoimmune diseases - Type 1 diabetes - Celiac disease - Rheumatoid arthritis - MS - SLE Allergy Epilepsia Obesity Hernia inguinalis Pylorostenosis Migraine
Ökad risk för Typ 1 diabetes: HLA DR 3,4 ; DQ 2, 8 Minskad risk: DR 2 ; DQ 6, men en del av dessa får diabetes! 20-40% av befolkningen har genetisk ökad risk att få/kunna få Typ 1 diabetes, men <1% får sjukdomen! Miljön avgör! Johnny Ludvigsson
Major susceptible HLA genotypes. a. DR4- DQA1*0301-DQB1*0302 / DR3- DQA1*0501-DQB1*0201 b. DR4- DQA1*0301-DQB1*0302 / DR4- DQA1*0301-DQB1*0302 c. DR4- DQA1*0301-DQB1*0302 / DR8- DQA1*0401-DQB1*0402 d. DR3-DQA1*0501-DQB1*0201 / DR3-DQA1*0501-DQB1*0201 e. DR4- DQA1*0301-DQB1*0302 / DR4- DQA1*0301-DQB1*0201 f. DR4- DQA1*0301-DQB1*0302 / DR1 # - DQA1*0101-DQB1*0501 g. DR4- DQA1*0301-DQB1*0302 /DR13-DQA1*0102-DQB1*0604 h. DR4- DQA1*0301-DQB1*0302 / DR4- DQA1*0301-DQB1*0304 i. DR4- DQA1*0301-DQB1*0302 / DR9- DQA1*0301-DQB1*0303 j. DR3- DQA1*0501-DQB1*0201 / DR9- DQA1*0301-DQB1*0303 Swedish patients: a + b + d + g = 73%
Tissue Type - based on HLA antigens (heterodimeric proteins) on cell surfaces. Class I: directs CD8 T cells to target cell Class II: antigenpresentation to CD4+ T cells
Type 1 diabetes loci http://www.t1dbase.org/
Genetics of Type 1 diabetes HLA IS BY FAR THE MOST IMPORTANT GENETIC FACTOR! Non-HLA genes contribute to ~ 40% of the genetic risk:» INS VNTR - poor immune tolerance induction» CTLA-4 - reduced levels of regulatory T cells?» ITPR3 - beta cells more vulnerable to stress??» MHCT2: less expression of HLA class II proteins New genes soon! The 500 000 SNP array almost done by the T1DGC.
Type 1 diabetes - islet autoimmunity genetic interaction 1 HLA INS VNTR INS VNTR Chromosome 11 Case-Control (1982) 3-4% added risk.
Type 1 diabetes - islet autoimmunity genetic interaction 2 HLA INS VNTR CTLA-4 CTLA-4 Chromosome 2 sib-pair linkage (1996) 2-3%
Type 1 diabetes - islet autoimmunity genetic interaction HLA INS VNTR INTERACTION CTLA-4 ITPR3 MHC2TA PTPN22
Oncogenesis point mutation in a coding exon translocation resulting in loss of normal gene suppression or synthesis of an altered gene product eg Burkitt lymphoma gene amplification eg neuroblastoma loss of an anti-oncogene eg retinoblastoma, Wilm s tumour
Gene Therapy Gene insertion, physical methods Gene insertion, viral vectors Gene targeting; homologues recombination
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