Faculty of Biochemistry and Molecular Medicine: Molecular, cell biological and genetic aspects of diseases

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1 1 Faculty of Biochemistry and Molecular Medicine: Molecular, cell biological and genetic aspects of diseases Inheritance patterns II 2 Mitochondrial (lectured by Alex) Multifactorial inheritance 2 Untypical ways of inheritance 6 Glossary of terms 13 Sanna Karppinen

2 4. Inheritance patterns II: Multifactorial inheritance Despite accidents and typical infections heritable elements are involved in all diseases Congenital malformations, common adulthood diseases The amount of genetic and environmental factors varies Appear in families or in certain population, but inheritance doesn t follow any pattern polygenic vs. multifactorial? 100% GENETIC FACTORS 2 ENVIRONMENT

3 4. Inheritance patterns II: Multifactorial inheritance 3 Monogenic vs Multifactorial In multifactorial diseases inheritance pattern is not so clear, because many genes and environmental factors affect the manifestation Pathogenic mechanisms are complicated Etiologic heterogenity: Same or similar phenotype may originate from different factors

4 S. Solovieva 4. Inheritance patterns II: Multifactorial inheritance 4 Multifactorial diseases Effect of many genes Gene - Gene+ Gene + Disease phenotype Gene - Gene + Gene + Activity other Stress Smoking Environmental factors

5 4. Inheritance patterns II: Multifactorial inheritance Example of epistasis Coat color is controlled by two genes: E gene: pigment (feomelanin) or no pigment works first B gene: the amount of pigment (eumelanin) effect depends on E gene 5 These two genes are epistatic, which means that the expression of one of the genes is dependent upon the expression of the other.

6 4. Inheritance patterns II: Untypical ways of inheritance 1. DNA repeat expansions and human diseases (will be lectured as own topic later) anticipation = the symptoms of the genetic disorder appear younger and severity of symptoms increases in each generation 2. Genomic imprinting Expression of a gene is regulated by a parent-of-originspecific manner The activity of a gene in a genepair depends on whether the gene locates in maternal or paternal chromosome Methylation of other allele during female/male meiosis: methylated gene is inactivated May result in disease, if the only active allele is inactivated or deleted Many are tissue specific About 100 genes known, as large groups in genome (e.g. genes encoding RNA modifying proteins, proteins regulating tissue growth and brain functions) CH 3 6

7 4. Inheritance patterns II: Untypical ways of inheritance Genomic imprinting Prader-Willi (PWS) ja Angelman (AS) syndromes frequencies 1: Congenital multi-anomaly syndromes Genes of the syndromes locate in the same chromosomal region 15q11-12, 6 imprinted genes Paternal deletion in region 15q11-12 causes Prader-Willi syndome and maternal deletion Angelman s syndrome In PWS patients, deletion in paternal chromosome, mother s chr inactivated (four paternally expressed genes) In AS patients, deletion in maternal chromosome, father s chr inactivated (two maternally expressed genes) 7 CH 3 PWS AS CH 3

8 4. Inheritance patterns II: Untypical ways of inheritance Genomic imprinting: Prader-Willi (PWS) ja Angelman (AS) syndromes 8 ATP10A + Prader-Willi syndrome (PWS): PWS genes normally paternally active, maternal inactive Deletion in paternal allele or both alleles are inherited from mother (UPD) disease mild to moderate intellectual impairment and learning disabilities, obesity, hypogenitals Angelman syndrome (AS): Normally maternal gene active, paternal inactive Deletion in maternal allele, or both alleles are inherited from father (UPD) disease delayed development, intellectual disability, severe speech impairment, and problems with movement and balance

9 4. Inheritance patterns II: Untypical ways of inheritance 9 X-chromosomal inactivation = Lyonization About two weeks of age in every cell of a female embryo, one of the two X chrs are inactivated Guarantees equal gene dosages both in males and females X chr is silenced by packaging it into a transcriptionally inactive structure called heterochromatin irreversible cell herited, similar in every daughter cell (Reversed during oogenesis) Females are mosaics: in some cells genes from paternal X-chromosome are expressed and in other cells those from maternal X chr If one X-chr contains mutation, part of the cells still have normal allele and gene function Not all X-chromosomal genes are inactivated homologs in Y chr X-chromosomal inherited diseases: due to abnormal inactivation, a woman carrying X chr recessive trait may manifest the disease (if one X is mutated and the one with normal allele is

10 4. Inheritance patterns II: Untypical ways of inheritance 10 Other mechanisms of untypical inheritance: Prion diseases (will be lectured as own topic later) Gonadal/germ line mosaikism Parent may have mutation in gonads as a mosaic, so that among the normal germ line cells there is a cell line with altered genome Uniparental disomy (UPD) Person has two copies of a chromosome from one parent and no copy from the other parent Arises from a meiotic chromosome segration defect (nondisjunction I/II) May cause a disease in the case of imprinted genes

11 4. Inheritance patterns II: Untypical ways of inheritance 11 Uniparental disomy (UPD) Trisomy rescue (loss of one homologue) can lead to UPD UPD can arise also in fertilization, if one gamete is disomic and other nullisomic for same chromosome Child can be homozygous for recessive trait, eventhough only one parent has the gene defect being healthy carrier Cystic fibrosis

12 12 Questions How many genes human have? What are the different mutation types? What consequences different kind of mutations in the protein encoding area may have in the amino acid level? For example a) an insertion or b) a deletion? What means a) a causative mutation, b) a polymorphism, c) a multifactorial disease? What is the risk for a child to inherit a disease in the case of a) autosomal recessive trait when both parents are healthy carriers; b) autosomal dominant trait when one parent is affected? Justify e.g. with a picture. What are the characteristics of X chromosomal inheritance? What factors can confuse the determination of an inheritance pattern? Genomic imprinting, how does it affect disease phenotype? What means lyonisation? What means uniparental disomy and how it arises?

13 13 Glossary of terms gene locus allele genotype phenotype homozygous (AA, aa, +/+, -/-) heterozygous (Aa, +/-) dominant recessive autosomal Gene locus 2 alleles

14 14 Glossary of terms penetrance polymorphism X-chromosomal carrier pedigree mitochondrial inheritance monogenic polygenic (multifactorial inheritance) epistasis

15 15 Faculty of Biochemistry and Molecular Medicine: Molecular, cell biological and genetic aspects of diseases 5 ECTs Chromosomal mutations and disorders Sanna Karppinen

16 16 Content of the lecture: Chromosomal mutations and disorders 17 Chromosome/genome number changes 18 Errors in the division of chromosomes 22 Autosomal chromosomes 22 Sex chromosomes 32 Structural abnormalities of chromosomes 37 Questions 50 Aims for this part: learn the most common chromosomal disorders related to number changes of autosomes and sex chromosomes get familiar with the different kind of chromosomal mutations and learn how they arise

17 4. Chromosomal diseases Chromosomal abnormalities: microscopically detectabele change in karyotype Chromosomal diseases: Chromosomal abnormalities lead to excess or loss of genetic material causing harm for the function or healthiness of tissue, organ or individual Congenital abnormalities, but usually not inheritable Develope during fertilisation or before it Frequency: 50% of abortions during first trimester show chromosomal anomaly 0.6% of the live-born have chromosomal anomaly Numerical abnormalities Structural abnormalities % of newborns have a chromosomal anomaly with symptoms 0.2% symptoms during childhood or teenage 0.2% symptomless changes

18 4. Chromosomal diseases: number changes 18 Diploid (2N) Normal set of metaphase chromosomes Aneuploidy Nullisomic (2N-2) Monosomic (2N-1) Aneuploidy= abnormal number of chromosomes extra or missing chromosome(s) numerical abnormality Double monosomic (2N-1-1) Trisomic (2N+1) Tetrasomic (2N+2)

19 4. Chromosomal diseases: number changes Variations in number of complete chromosome sets Normal chromosomes 19 Diplod (2N) Monoploid - only one set of chromosomes (haploid) Monoploid (N) Polyploid - tree or more sets of chromosomes Triploid (3N)) Tetraploid (4N)

20 4. Chromosomal diseases: number changes Somatic cell: diploid 2N Gamete: haploid 1N Some somatic cells are polyploidic: megakaryocytes (16-128n) Polyploidy seems to increase the development of platelets hepatocytes (4n-8n) Reason is not understood: prabably for protection of genetic material or gene expression Muita kudoksia: cardiomyocytes (4n) big trofoblasts (8n-64n) Purkinjen cells (4n) Retinal ganglion cells (4n) 20 Cancer cells contain clonal chromosomal abnormalities muscle cells may contain even hundreds of diploid nuclei in one cell

21 4. Chromosomal diseases: number changes 21 Genome number changes are harmful for embryo development Triploidy (3n = 69) may occur, if diploid premature egg cell is fertilised, or haploid egg is fertilised by two sperm cells at the same time Molar pregnancy (non-viable fertilized egg implants in the uterus and will fail to come to term) may occur from a tsygote having two paternal and no maternal genome Ovarial teratoma: tumor having a diploid egg, which starts to divide parthenogenetically Chimera: fusion of two fertilised tsygotes While in monotsygote twins the tsygote divides to form two embryos developing in uterus separately

22 4. Chromosomal diseases: number changes, errors in the division of chromosomes Autosomes 22 Single number differences of chromosomes (aneuploidy) are the most common reasons for both miscarriages and for chromosomal disorders Defect in meiosis (nondisjunction) leads to gamete having one chromosome too much or missing one chromosome if this cell participates in fertilisation, the result is trisomy (2n=47) tai monosomy (2n=45) for the corresponding chromosome If the defect occurs later transmitted to progeny mosaicism Female meiosis is long prone to chromosomal abnormalities Trisomies for chromosomes 13, 18 and 21 are found in live-born babies (and rare mosaics of trisomies for chromosomes 8 and 9) Meiosis I Meiosis II TRISOMY Meiosis I Meiosis II fertilisation MONOSOMY

23 trisomic monosomic 4. Chromosomal diseases: number changes, errors in the division of chromosomes 23 First meiotic division Defect in I meiotic division: Chromosome pair in same pool diploid ja nullisome gametes Errors at meiosis I are the most common cytologic explanation for trisomies. Most trisomies show a maternal age effect, and the advanced maternal age correlates positively with errors at meiosis I 90% chr. 13 ja 21 trisomies: maternal, generally defects in meiosis I gamete

24 4. Chromosomal diseases: number changes, errors in the division of chromosomes 24 Second meiotic division Defect in II meiotic division : One extra chromosome or one chromosome loss Errors at meiosis II are less common among aneuploidies. 90% chr.18 trisomies maternal 2/3 defects in meiosis II gamete trisomic monosomic normal

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26 4. Chromosomal diseases: number changes, errors in the division of chromosomes 26 Trisomy 21, Down syndrome incidence 1:600 often defect in the I division of meiosis, in 80-90% cases maternal The age of mother correlates with the risk of trisomy-21 about 5 % of the Down patients have trisomy mosaicism, translocation or other structural defect in the chr 21 Mosaics have milder symptoms

27 4. Chromosomal diseases: number changes, errors in the division of chromosomes 27 Exercise 5. Why mother s age is associated with higher risk of for a baby to have chromosome anomalies than with father s age?

28 4. Chromosomal diseases: number changes, errors in the division of chromosomes 28 Trisomy 21, Down syndrome Critical genes for the syndrome locate in region 21q22 21q22.1-q22.3: 289 genes DSCR1 (Down Syndrome Critical Region gene1): causes intellectual disability and heart defects Overexpressed in brains of Down fetuses DSCR4: affects development of morphologic features, hypotonia and intellectual disability Expressed mainly in placenta Severity of symptoms vary, life time about 40 years (~ 50%) Intellectual disability, fastened aging Infections, heart problems (not all), dysfunction of intestinal tract Females are fertile, men not

29 4. Chromosomal diseases: number changes, errors in the division of chromosomes Trisomy 21, Down syndrome Function of DSCR1 Protein affects the transcription of genes by inhibiting the calsineurin dependent signaling pathway and thus possibly disturbs the development of central nervous system 29 Normal Nature 441, (1 June 2006) Down syndrome DSCR1 and also DYRK1A

30 4. Chromosomal diseases: number changes, errors in the division of chromosomes 30 Trisomy 13, Patau syndrome 1/ In 75% of cases extra chr. 13 translocation 20%, some inherited mosaic 5%, incomplete extra chromosome Lethal or severe developmental defect Microcephaly Cleft lip and palate failure of the forebrain to divide properly Severe heart defect Abdominal, genital and kidney defects Survival about 1-2 months

31 4. Chromosomal diseases: number changes, errors in the division of chromosomes 31 Trisomy 18 / Edwards syndrome More common that trisomy 13, 1: 5000 ~ 95 % clear trisomies and 5 % mosaic cases Partial trisomy 18 due to translocation (~2%) Smallest extra region of chr.18 that causes the syndrome is q21-22 Brain anomalies, Microcephaly severe developmental disbility Heart defects (~90%) clenched hands rocker bottom feet lifetime1-2 months, death latest at 1year of age

32 4. Chromosomal diseases: number changes, errors in the division of chromosomes Sex chromosomes 32 Single number changes or structural abnormalities of sex chromosomes are less harmful than those in the other chromosomes Mostly do not harm embryo development but appear later in the life Y chromosome contains low number of genes Inactivation of X chromosome Sex chromosomes, X and Y, determine the genetic characteristics of sex-linked traits SRY-part (pter-q11.2) of Y contains genes that direct the development of the masculine features without femine phenotype mild developmetal disoders, even harmless, symptoms during childhood or at teenage Sex chromosome abnormalities In men: 47,XXY (Klinefelter syndrome) 47, XYY 46,XY/45,X-mosaicism In women: 45,X-monosomy (Turner s syndrome) 47,XXX 48,XXXX and 49,XXXXX 46,XY-women

33 4. Chromosomal diseases: number changes, errors in the division of chromosomes 33 Sex chromosomes X and Y share sequence homology segments, pseudoautosomal regions (PAR1, 2, 3) European Journal of Human Genetics (2008) 16, SRY inherited in the same manner as autosomes in males, pairing and recombination are restricted to the PARs Deletion of PAR1 is associated with total male sterility Reduced recombination in PAR1 can lead to aneuploid sperm, which can cause X-chromosome monosomy (Turner syndrome) or XXY (Kleinfelter syndrome) in the offspring recombination is necessary in males

34 4. Chromosomal diseases: number changes, errors in the division of chromosomes 45, X Turner s syndrome 34 45, X, mosaicism mosaicism allow the survival in utero: placental rescue cell line 46, XX loss of genes in PAR1 affect development of placenta lethality Incidence 1: 2500 newborn girls, more common in miscarriages (8.6% vs 0.04%) Poorly developed, fibrotic gonads lack of germ cells and ovarian follicles no oocytes Activity of two active X chrs are needed to maintain the germ cells and later ovaries No estrogen synthesis lack of female features No puberty without hormone therapy (estrogen and progesterone) Somatic abnormalities due to abnormal dosage of PAR genes Short stature (<150 cm) SHOX important for bone development and growth Lymphedema of the hands and feet, heart defect

35 4. Chromosomal diseases: number changes, errors in the division of chromosomes 35 47, XXY Klinefelter syndrome Most common sex chromosome alteration in males 47, XXY 1: newborn males 48, XXXY, or 49, XXXXY: variant forms more severe signs and symptoms Extra copies of X chromosome are inactivated Extra copies of genes on the X chr. interfere with male sexual development often prevent testes to function normally reduce the levels of testosterone Affects male physical and cognitive development Infertile, small testes Slightly feminized physique (breast development, wide hip) Poor muscle tone Tall stature Some have learning and psychological problems Testosterone treatment to improve musculine phenotype, concentration and strenght Not inherited

36 4. Chromosomal diseases: number changes, errors in the division of chromosomes 36 47, XYY 1:1000 newborn males Affected usually very tall severe acne during adolescence Fertility and sexual development are normal normal physical appearance May include learning disabilities and behavioral problems such as impulsivity Not inherited

37 4. Chromosomal diseases: Structural abnormalities of chromosomes 37 Structural abnormalities of chromosomes DNA damage is common phenomenon in living cells damage occuring during DNA replication or recombination event may remain unrepaired or is repaired incorrectly Types of structural abnormalities : Balanced: translocations, inversions Unbalanced: deletions, duplications, insertions (occur in all chromosomes) Can be inherited, % unbalanced gametes in meiosis disease to progeny Geno- and phenotype depends on how the genetic material of the parents is divided in meiosis Of the clinically relevant cases 1/3 are new alterations, 2/3 inherited

38 4. Chromosomal diseases: Structural abnormalities of chromosomes 38 Translocations Translocations involve the breakage and rejoining of two or several chromosomes In balanced translocation there is an equal exchange of chromosomal material Reciprocal translocation: the location of a gene changes, but the amount of genetic material is unaltered Doesn t usually cause problems for a carrier, but a progeny may be affected Most often either normal or translocation carrier chromosomes are inherited Other distributions lead to non-balanced chromosomes miscarriage

39 4. Chromosomal diseases: Structural abnormalities of chromosomes 39 Examples of translocations t(1;8)(q32;q22) In Finnish families, > in 10 generations Causes miscarriage in 30 % of the pregnancies of carriers No chromosomal diseases have been observed in the family t(4;11)(q21;p13) Normal, can cause problems for progeny (mixed lineage leukemia)

40 4. Chromosomal diseases: Structural abnormalities of chromosomes Example: t(4;11)(q21;p13): meiosis 40 Translocation chromosomes have aligned with homologous chromosome segments in the division plane and a tetravalent is formed. What kind of segregation possibilities there are in the I division? Normal situation Jukka Moilanen (

41 4. Chromosomal diseases: Structural abnormalities of chromosomes Example: t(4;11)(q21;p13): meiosis 41 A alternate type B adjacent 1 type (frequent) C adjacent 2 type, (rare): normal T carrier Extra 4 11 deficiency Extra 11 4 deficiency Extra 4 11 deficiency Extra 11 4 deficiency (A) alternate type balanced chromosomes in gametes produces normal gametes, or gametes with the parental balanced translocation. The baby will have a normal phenotype. (B, C) adjacent types Association of normal chromosome with rearranged gives rise to "duplication-deficiency": an excess of some bits and a lack of other bits changes in the amount of genes

42 4. Chromosomal diseases: Structural abnormalities of chromosomes Robertsonian centric translocation Specific type of translocation: fusion of 2 acrocentric chromosomes (chr 13, 14, 15, 21, 22) Long arms fuse very close to the centromeres rearranged chromosome includes the long arms (translocation chromosome containing the short arms is lost) no phenotypic effect, a carrier has 45 chromosomes but gene dosage does not change 42 Frequency 1:1000 t(13;14)(p10;q10) carriers 1:1500 Predisposes to trisomy 13 ja miscarriage, mild infertility t(14q;21q), most frequent In carrier pregnancies 20% risk for extra copy of chr. 21 (Down syndrome) lost

43 4. Chromosomal diseases: Structural abnormalities of chromosomes Meiosis in the carrier of Robertsonian transloction t(14;21) Carrier of the translocation is phenotypically normal, but has deficiency in fertility Carrier may produce six different types of gametes 1/6 of the gametes have normal chromosomes, 1/6 has translocation chr and four are aneuploids Chr 14 Chr Normal chromosomes I division I division I division Balanced 14/21 carrier 14/ Possible gametes Results in Normal 14/21 Carrier 14/21 21 Extra 21 Down deficiency Lethal deficiency Lethal 14/21 14 Extra 14 Lethal

44 4. Chromosomal diseases: Structural abnormalities of chromosomes Chromosomal abnormalities have a role in cancer cell development t(9;22), Philadelphia chromosome Many known pathological translocations are balanced resiprocal translocations Philadelphia chromosome: resiprocal translocation between chr 9 ja 22 t[9,22][q34;q11] BCR-ABL fusion gene (breakpoint cluster region Abelson leukemia viral proto-onkogene) uncontrollable division of cells, leukemia found only in cancer cells 44 44

45 4. Chromosomal diseases: Structural abnormalities of chromosomes Translocations in cancer: Translocation t(8;14)(q24;q32) t(11;14)(q13;q32) t(14;18)(q32;q21) t(10;(various))(q11;(various)) t(2;3)(q13;p25) t(8;21)(q22;q22) t(9;22)(q34;q11) Philadelphia chromosome Associated diseases Burkitt's lymphoma Mantle cell lymphoma Follicular lymphoma (~90% of cases) Papillary thyroid cancer Follicular thyroid cancer Acute myeloblastic leukemia with maturation Chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL) t(15;17)(q22;q21) Acute promyelocytic leukemia 45 Fused genes/proteins First Second c-myc on chromosome 8, IGH (immunoglobulin heavy locus) on gives the fusion protein chromosome 14, lymphocyte-proliferative ability induces massive transcription of fusion protein cyclin D1 on chromosome 11, IGH (immunoglobulin heavy locus) on gives fusion protein cellproliferative chromosome 14, ability induces massive transcription of fusion protein IGH (immunoglobulin heavy locus) on chromosome 14, induces massive transcription of fusion protein RET proto-oncogene on chromosome 10 PAX8 - paired box gene 8 on chromosome 2 ETO on chromosome 8 Bcl-2 on chromosome 18, gives fusion protein anti-apoptotic abilities PTC (Papillary Thyroid Cancer) - Placeholder for any of several other genes/proteins PPARγ1 (peroxisome proliferator-activated receptor γ 1) on chromosome 3 AML1 on chromosome 21 found in ~7% of new cases of AML, carries a favorable prognosis and predicts good response to cytosine arabinoside therapy Abl1 gene on chromosome 9 [15] BCR ("breakpoint cluster region" on chromosome 22 PML protein on chromosome 15 RAR-α on chromosome 17 persistent laboratory detection of the PML- RARA transcript is strong predictor of relapse t(12;15)(p13;q25) Acute myeloid leukemia, congenital fibrosarcoma, secretory breast carcinoma, TEL on chromosome 12 TrkC receptor on chromosome 15 mammary analogue secretory carcinoma of salivary glands t(9;12)(p24;p13) CML, ALL JAK on chromosome 9 TEL on chromosome 12 t(12;21)(p12;q22) ALL TEL on chromosome 12 AML1 on chromosome 21 t(11;18)(q21;q21) MALT lymphoma API-2 MLT t(1;11)(q42.1;q14.3) Schizophrenia t(2;5)(p23;q35) Anaplastic large cell lymphoma ALK NPM1 t(11;22)(q24;q ) Ewing's sarcoma FLI1 EWS t(17;22) dermatofibrosarcoma Platelet derived growth factor B on Collagen I on chromosome 17 protuberans chromosome 22

46 4. Chromosomal diseases: Structural abnormalities of chromosomes Unbalanced translocation 46 Unequal exchange of chromosome material extra or missing genes = deletions and duplications Extra gene material (>4%) or missing material (>2%): miscarriage Small alteration (microdeletion/ duplication): chromosome disease Usually sporadic, with mild phenotype, inheritable changes Deletions of short arm of chr. 4 and 5: intellectual disability Prader-Will: 15q11-13 paternal deletion intellectual disability, over-weight, special features Angelman syndrome: 15q11-13, maternal deletion severe intellectual disability, epilepsy, anxiety, special features

47 4. Chromosomal diseases: Structural abnormalities of chromosomes Inversions If two breaks occur in one chromosome the region between the breaks may rotate 180 degrees before rejoining with the two end fragments the overall amount of the genetic material is not changed inv9(p11;q13), most common in general population, 1-3%, always inherited as an balanced form no recombination clinically irrelevant Clinically relevant appear in the cases of infertility or phenotypically abnormal child 47

48 4. Chromosomal diseases: Structural abnormalities of chromosomes 48 Inversions Recombination doesn t happen in short inversion In long inversions, inversion chromosome aligns with homologous chromosome inversion loop crossing-over deletions or duplications

49 2. Changes in the genome 49 Inversion makes a break in gene hemofilia A J Genet Med Jun;7(1):1-8

50 Questions 50 What means a) trisomic, b) triploid? What effects can extra chromosomal material have? What kind of number changes of autosomes are found in live-born babies? What kind of consequence has nondisjunction a) in the first b) in the second meiotic division? What means Robertson s translocation? How can be a Down syndrome inherited from a parent to child? What happens in reciprocal translocation? What means unbalanced translocation? What is a Philadelphia chromosome?