Identification of simultaneous mutation of fibrinogen alpha chain and protein C genes in a Japanese kindred

Afibrinogenaemia usually induces a bleeding tendency during infancy, whereas protein C deficiency increases susceptibility to thrombosis in children or adolescence. Mutations of these genes have been, therefore, established as independent risk factors for coagulation disorders. We describe the homozygous mutation of the fibrinogen alpha chain gene and additional heterozygous mutation of the protein C gene in a male infant who showed prolonged umbilical bleeding after birth. On examination, the plasma fibrinogen was undetectable, and the activity and antigen level of protein C were reduced. The patient showed no fibrinogen Aalpha chain as well as Bbeta and gamma chains by Western blotting. The sequencing analysis showed the homozygous deletion of 1238 bases from intron 3 at position 2008 to intron 4 at position 3245 in the fibrinogen alpha chain gene. Both parents were heterozygous carriers of this mutation. In this patient, an additional mutation was also detected in the protein C gene: the heterozygous deletion of exon 7 at position 6161-6163 or 6164-6166, resulting the deletion of one amino acid (Lys150 or 151). His mother was also a carrier of this mutation. As the simultaneous mutation of the fibrinogen alpha chain and protein C genes has not been previously reported, the influence of the interaction between these two mutations on the clinical manifestations of this patient should be carefully monitored for a long period.

Mesenteric venous thrombosis in hereditary protein C deficiency with the mutation at Arg169 (CGG-TGG)

A 39-year-old man with no significant medical history was admitted to our hospital with severe abdominal pain and melena. Computed tomographic (CT) scans demonstrated superior mesenteric venous thrombosis. Although thrombolysis and anticoagulant therapy was started immediately, symptoms of strangulation ileus developed. Laparotomy was therefore performed and revealed necrotic stenosis of the ileum. The patient, his father and sisters showed low protein C levels. Direct sequencing analysis of their protein C gene revealed a heterozygous mutation at codon 169 corresponding to the cleavage site of the activation peptide, which was referred to as protein C Tochigi.

Chronic disseminated intravascular coagulation and childhood-onset skin necrosis resulting from homozygosity for a protein C Gla domain mutation, Arg15Trp

A toddler of Haitian descent presented with an 18-month history of chronic consumption coagulopathy, followed by catastrophic skin necrosis. Protein C deficiency (1% to 3% of control) was noted by functional assay; chromogenic assay and antigen levels were 30% of control. Plasma infusion abrogated the disseminated intravascular coagulation-like state. The authors identified a homozygous mutation, C1432T, resulting in a missense, Arg15Trp, in the gamma-carboxyglutamate domain of the protein. Chronic consumption coagulopathy without purpura fulminans or venous thrombosis is a rare presentation of defective protein C pathway. The result of this mutation is a mixed type I (low antigen) and type II (low function) phenotype.

Screening for inherited thrombophilia: indications and therapeutic implications

BACKGROUND AND OBJECTIVES

In recent years knowledge concerning inherited and acquired causes of thrombophilia has increased greatly. The most common inherited traits (deficiency in antithrombin, protein C, or protein S, factor V Leiden, prothrombin G20210A) and mild hyperhomocysteinemia are diagnosed in at least 40% of patients with venous thromboembolism (VTE).

INFORMATION SOURCES

The authors work in this field, contributing to multicenter clinical and laboratory investigations and to peer-reviewed journals with original papers. The material examined in this review includes articles published in journals covered by MedLine.

STATE OF THE ART

The associated risk for VTE is different according to genotype, being higher among the carriers of natural anticoagulant deficiencies and homozygotes for factor V Leiden. The overall prevalence of thrombophilic traits in the general population being near to 10% renders the probability of carrying multiple defects not excessively rare, with a further increase in thrombotic risk of up to 20-fold. Thus, clinical penetrance is heterogeneous, producing either mild or severe venous thrombotic manifestations, which can be unprovoked or associated with circumstantial risk factors and occur in either young or advanced age. More recently, inherited thrombophilia has been focused on as an important determinant of complications of pregnancy and puerperium. As expected, inherited thrombophilia produces an increased risk of VTE, particularly during puerperium. Moreover it is well established that thrombophilic women have an increased risk of late and/or recurrent fetal loss; whether they are at higher risk of pre-eclampsia, fetal growth restriction, and abruptio placentae is debated. Overall, 40% of women with obstetric complications other than VTE carry a thrombophilic trait. Yet, as a rule VTE and obstetric complications seem to occur in different individuals, probably because of the presence of unknown factors favoring one or other of these clinical manifestations.

CONCLUSIONS AND PERSPECTIVES

Inherited thrombophilia is now viewed as a multicausal model, the clinical event being the result of gene-gene and gene-environment age-dependent interactions; the associated clinical manifestations can be heterogenous as regards severity as well as type of event (VTE or obstetric complication). Therefore the criteria for screening affected individuals who have suffered from the above complications or their relatives should not be very stringent. The patient's genotype could be a main determinant of the features of primary or secondary prophylaxis used in the affected individual.

Protein C deficiency caused by homozygosity for a novel PROC D180G mutation--in vitro expression and structural analysis of the mutation

Homozygosity for a novel D180G mutation in the protease domain of protein C, associated with plasma protein C activity and antigen levels of 8% of normal was identified in a thrombosis prone family. Transient expression of protein C in HK-293 cells and analysis of protein C antigen in culture media and cell lysates showed that the secretion of mutant protein as compared with wild-type protein was reduced by 79% while the intracellular contents were similar. Computer analysis of the X-ray structure of activated protein C and of a theoretical model of the zymogen predicts that the mutation destabilises the molecule locally. Our results are compatible with a relatively unstable mutant molecule that could be trapped inside the cell and degraded. However, if secreted the mutant molecule could have a relatively normal catalytic activity and structure consistent with the plasma levels of protein C activity and the late onset of thrombosis.

Characterization of the human prostaglandin H synthase 1 gene (PTGS1): exclusion by genetic linkage analysis as a second modifier gene in familial thrombosis

Genetic evidence from a large Vermont kindred indicates that an unknown gene promotes thrombosis when inherited in conjunction with type I protein C deficiency. Cyclooxygenase-1 [prostaglandin H synthase 1 gene (PTGS1)] was tested as a plausible candidate for the unknown gene because of its role in primary hemostasis. The complete sequence of PTGS1 (25 638 nucleotides) was determined from a 37 kb human genomic cosmid clone to characterize intronic regions and subsequently to allow the search for mutations by direct sequencing of genomic DNA. Northern blot analysis confirms usage of a newly described distal poly-adenylation signal. Short tandem repeat (STR) sequences found in intron 2 and the 3' flanking region were developed as new genetic markers for PTGS1. The position of PTGS1 was refined on the CHLC chromosome 9 linkage map using the new markers scored in four Centre d'Etude du Polymorphisme Humain families and multipoint linkage analysis. Direct sequencing of DNA from members of the Vermont kindred led to the discovery of two new single nucleotide polymorphisms (SNPs) that give rise to non-conservative amino acid changes in the signal peptide (Arg(8) to Trp and Pro(17) to Leu) of cyclooxygenase-1. Linkage analysis of the SNP and STR markers indicated that PTGS1 is not the interacting gene associated with an increased incidence of thrombosis in the Vermont kindred.

Multivisceral transplantation for portal hypertension and diffuse mesenteric thrombosis caused by protein C deficiency

BACKGROUND

Protein C is a vitamin K-dependent glycoprotein synthesized in the liver. Homozygous deficiency usually manifests as purpura fulminans in infancy and is often fatal. An unlikely, but potentially life-threatening, manifestation of protein C deficiency is mesenteric venous thrombosis.

METHODS

A patient with undiagnosed familial protein C deficiency and a history of intestinal infarction developed refractory duodenal and jejunal variceal bleeding as a result of diffuse visceral splanchnic thrombosis and portal hypertension. Because his life-threatening bleeding was unresponsive to all therapies, we performed multivisceral transplantation.

RESULTS

Multivisceral transplantation cured the patient's underlying disease and was lifesaving. Functional protein C, undetectable before transplantation, was normal after transplantation. He was discharged tolerating a normal diet and is alive at home 6 months later.

CONCLUSIONS

Multivisceral transplantation should be considered as a treatment option for patients with diffuse mesenteric thrombosis, even in the absence of short gut syndrome, when portal hypertension causes life-threatening complications unresponsive to less aggressive therapies.

Protein C/S ratio, an accurate and simple tool to identify carriers of a protein C gene mutation

Hereditary protein C deficiency is demonstrated by lowered protein C plasma levels in a patient and at least one first-degree relative. This approach is insufficient in some cases owing to overlapping protein C levels in carriers and non-carriers of a protein C gene mutation. The protein C/S ratio is a simple and more accurate tool to detect carriers. In four families, 62% of 29 carriers, compared with none of 39 non-carriers, were protein C deficient. Sensitivity and specificity of the protein C/S ratio were 90% and 92% respectively. The protein C/S ratio seems to be more accurate than the measurement of protein C levels alone to identify carriers of a protein C gene mutation.

Assessing the relative importance of the biophysical properties of amino acid substitutions associated with human genetic disease

The inclusion of a mutation in a pathology-based database such as the Human Gene Mutation Database (HGMD) is a two-stage process: first, the mutation must occur at the DNA level, then it must cause a clinically detectable disease state. The likelihood of the latter step, termed the relative clinical observation likelihood (RCOL), can be regarded as a function of the structural/functional consequences of a mutation at the protein level. Following this paradigm, we modeled in silico all amino acid replacements that could potentially have arisen from an inherited single base pair substitution in five human genes encoding arylsulphatase A (ARSA), antithrombin III (SERPINC1), protein C (PROC), phenylalanine hydroxylase (PAH), and transthyretin (TTR). These proteins were chosen on the basis of 1) the availability of a crystallographic structure, and 2) a sufficiently large number of amino acid replacements being logged in HGMD. A total of 9,795 possible mutant structures were modeled and 20 different biophysical parameters assessed. Together with the HGMD-derived spectra of clinically detected mutations, these data allowed maximum likelihood estimation of RCOL profiles for the 20 parameters studied. Nine parameters (including energy difference between wild-type and mutant structures, accessibility of the mutated residue, and distance from the binding/active site) exhibited statistically significant variability in their RCOL profiles, indicating that mutation-associated changes affected protein function. As yet, however, a biological meaning could only be attributed to the RCOL profiles of solvent accessibility and, for three proteins, local energy change, disturbed geometry, and distance from the active center. The limited ability of the biophysical properties of mutations to explain clinical consequences is probably due to our current lack of understanding as to which amino acid residues are critical for protein folding. However, since the proteins examined here were unrelated, and our findings consistent, it may nevertheless prove possible to extrapolate to other proteins whose dysfunction underlies inherited disease.

[Thrombophilias associated with cerebral venous thrombosis]

Many coagulation disorders have been associated with cerebral venous thrombosis. These disorders may be primary like protein C and S deficiency, antithrombine III deficiency and activated protein C resistance. Antiphospholipid antibodies represent an acquired disorders of coagulation. A prothrombotic state induced by more common factor including oral contraceptive, pregnancy and puerperium increases the venous thrombosis risk.

Inherited thrombophilia and first venous thromboembolism during pregnancy and puerperium

Venous thromboembolism is a rare but threatening complication of pregnancy. Little conclusive information is available on the actual risk of venous thromboembolism during pregnancy or puerperium in women with inherited thrombophilia, particularly in carriers of factor V Leiden and of the G20210A prothrombin gene mutation. To determine the pregnancy-related and puerperium-related risk of venous thromboembolism in women with inherited thrombophilia, we performed a case-control study on 119 women who had a first episode of deep vein thrombosis and/or pulmonary embolism during pregnancy or puerperium and 232 healthy women who had at least one pregnancy without thrombosis. Inherited thrombophilia was diagnosed in 47 patients (39.5%) and 15 controls (6.5%). The relative risk of venous thromboembolism was 10.6 (95% CI, 5.6-20.4) for heterozygous carriers of factor V Leiden, 2.9 (95% CI, 1.0-8.6) for heterozygous carriers of the prothrombin mutation and 13.1 (95% CI, 5.0-34.2) for those with antithrombin, protein C or protein S deficiency taken together. Sixty-eight of the 119 women (57%) had thrombosis after delivery, confirming the puerperium as a particularly high-risk period. When women were divided into two groups of those with antenatal or postnatal thrombosis. the relative risks associated with each type of inherited thrombophilia were of similar magnitude. In conclusion, women with inherited thrombophilia have an increased risk of venous thromboembolism during pregnancy. Among thrombophilic abnormalities, the prothrombin mutation was the weakest risk factor. Thrombosis occurred more frequently in puerperium than in pregnancy, whether or not thrombophilia was diagnosed.

Thrombophilia and immunological disorders in pregnancies as risk factors for small for gestational age infants

OBJECTIVES

To determine if inherited thrombophilia and immunological disorders represent risk factors for small for gestational age infants, and to assess their relationship with neonatal status.

DESIGN

Case-control study.

POPULATION

Ninety-seven consecutive women who had pregnancies complicated by unexplained small for gestational age infants, defined as a birthweight below the third centile and 97 women as controls who delivered infants with a birthweight > or = 10th centile.

METHODS

Patients were included in the immediate postpartum period and tested for antithrombin III, protein C, protein S, anticardiolipin and antinuclear antibodies, lupus anticoagulant, Factor V Leiden mutation, prothrombin 20210A mutation, and methylenetetrahydrofolate reductase (MTHFR) polymorphism. Women with small for gestational age infants were then divided into subgroups depending on haemostatic and immunologic status in order to compare neonatal events.

RESULTS

Frequencies for anticardiolipin and antinuclear antibodies were higher in women with small for gestational age infants compared with controls (P = 0.02 and P = 0.004, respectively), and overall prevalence of inherited thrombophilia were comparable in cases and controls (19.6% and 18.6%, respectively). The subgroups of patients with small for gestational age infants were women with only one inherited thrombophilia (n = 10), only one immunological disorder (n = 14), combined disorders (n = 9), and no detected abnormality (n = 64). Admission to paediatric ward significantly increased in the group with combined disorders (P = 0.002) compared with the other groups. Also one-third of the babies from this group had a poor neonatal outcome. However, most of the neonatal deaths (6/7 = 85.7%) occurred in the group with no detected abnormality.

CONCLUSION

The prevalence of inherited thrombophilia was considered to be similar between the case and the control groups even when immunological disorders were significantly elevated in pregnancies complicated by the baby being small for gestational age. Combined disorders may represent a potential risk factor for severe small for gestational age infants. However, the aetiology of small for gestational age infants with poor neonatal outcomes remains unknown in most cases.

Low level of circulating activated protein C is a risk factor for venous thromboembolism

The levels of circulating activated protein C (APC) reflect in vivo protein C activation. The aim of this study was to determine whether a low APC level is an independent risk factor for venous thromboembolism (VTE). We measured APC in 160 patients with a history of VTE and without recognized thrombophilic defects, and in 199 healthy individuals. The mean (+/- SD) APC level was lower in patients (0.99 +/- 0.44 ng/ml) than in controls (1.19 +/- 0.41 ng/ml) (p < 0.0001), and showed a different distribution in the two groups. Thirty-eight patients (23.7%) had APC levels below the 5th percentile of the control group (<0.69 ng/ml) and 57 patients (35.6%) had APC levels below the 10th percentile (<0.77 ng/ml). APC levels <0.69 ng/ml increased the risk of a single or recurrent episode of VTE 4.2-fold (95% confidence interval, 2.0-9.0) or 6.9-fold (2.6-17.9). respectively, and APC levels <0.77 ng/ml increased these risks 3.4-fold (1.9-6.2) or 5.1-fold (2.3-11.2), respectively, compared with controls. Familial studies revealed that in some cases the low APC phenotype seems to be hereditary. We conclude that a low level of circulating APC in individuals without any of the most recognized thrombophilic defects is a prevalent, independent risk factor for VTE, and that it predisposes to recurrent VTE.

Abnormal propeptide processing resulting in the presence of two abnormal species of protein C in plasma: characterization of the dysfunctional protein C Padua3 (protein C(R-1L/propeptide))

A heterozygous G-->T transversion at position 1388 of the protein C (PC) gene which predicted the substitution of Arg(-1) to a Leu (PC(R-1L)) was identified in a thrombophilic patient. The PC(R-1L) was purified from the patient's plasma by immunoaffinity chromatography using Ca++-independent and Ca++-dependent monoclonal antibodies. NH2-terminal sequencing of the light chain of PC(R-1L) revealed two amino acid sequences: one was identical to the complete propeptide sequence of PC, while the other matched the normal PC light chain sequence elongated by one amino acid (Leucine at position 1). Activated PC(R-1L/propeptide) exhibited normal amidolytic and impaired anticoagulant activity. Thus, the substitution of a Leu for an Arg at position -1 of PC shifts the propeptidase cleavage site by one amino acid. In addition, in PC(R-1L/propeptide) the propeptide cleavage at Lys(-2) is less efficient since approximately 60% of PC variant molecules present in patient's plasma retained the entire propeptide. Our findings suggest that depending on the specific amino acid substitution at position-1, PC can be secreted in plasma containing the entire propeptide attached to the light chain. Impaired interaction of elongated APC molecules with a membrane-surface and/or factor Va which is the physiological substrate for APC, is manifested in vivo by thrombophilia.

Neonatal purpura fulminans due to homozygous protein C deficiency

Severe and recurrent purpura fulminans developed in a Turkish boy at 1 week of age. Initial coagulation studies performed were compatible with disseminated intravascular coagulation. Subsequent investigations showed that the patient had homozygous and his healthy parents had heterozygous protein C deficiency. The episodes of purpura fulminans were controlled by infusions of fresh frozen plasma and heparinization. Oral anticoagulant therapy was given in the symptom-free period.

Foetal growth restriction in children with prothrombotic risk factors

Placental infarction is frequently observed in low birth weight children. To evaluate whether low birth weight in healthy term neonates is associated with foetal inherited prothrombotic risk factors this retrospective study was conducted. Outcome measures were "birth weight in the lowest quartile" and "birth weight in the lowest decile" in singletons with a gestational age of > or =37 weeks. The analyses were based on 375 Caucasian children screened at the Monster childhood thrombophilia centre with complete data for all prothrombotic risk factors (factor V G1691A, prothrombin G20210A, elevated lipoprotein (a), protein C-, protein S-, antithrombin-deficiency). The proportion of children in the lowest birth weight quartile increased from 23.7% to 30.5% to 48.0% for children with no, only single heterozygous and multiple or homozygous defects respectively. The respective adjusted odds ratios (95% confidence intervals) of thrombophilia for birth weight in the lowest quartile (lowest decile) were 1.53 (0.76-3.08) in carriers of one prothrombotic risk factor and 4.01 (1.48-10.84) in subjects carrying multiple or homozygous defects. We identified foetal thrombophilia as an additional cause of low birth weight.

Silent cerebral infarcts in basal ganglia are advanced in congenital protein C-deficient heterozygotes with hypertension

Congenital protein C deficiency is now widely recognized as a genetic risk for venous thrombosis. However, it remains uncertain whether this condition also confers risk for arterial thrombosis. We evaluated the association of congenital protein C deficiency with hypertension and silent cerebrovascular disease using brain magnetic resonance imaging (MRI) (T1- and T2-weighted and proton density images) in a large family pedigree of protein C deficiency diagnosed by gene analysis, compared with 46 non-pedigree related control subjects with normal protein C levels (> or = 75%) who were selected from among 55 asymptomatic hypertensive subjects matched for age and cardiovascular risk factors. Of the 58 living subjects in this pedigree, we measured plasma protein C levels in 45 subjects, and found 2 cerebral infarctions in the 24 heterozygotic subjects, whereas there was no stroke in the 21 normal homozygotic subjects. We performed brain MRI in 14 asymptomatic hypertensive subjects without any cardiovascular disease and in two patients with cerebral infarction, and found 28 cerebral infarcts (two corresponded to the patients' neurologic deficits and 26 were silent). All were lacunar infarcts < 10 cm in size. A total of 25 silent lacunar infarcts were found in nine heterozygotic subjects, whereas only one was found in the seven normal homozygotic subjects (2.8 v 0.14 lacunes per person, P = .002). No advanced white matter hyperintense lesions in T2-weighted images were found in either group. The prevalence of silent lacunar infarcts in the heterozygotic subjects was also significantly higher than that in normal control subjects (1.0 per person, P = .01). Concerning the distribution of silent infarcts, the number of lacunes located in the basal ganglia was higher in the heterozygotic subjects (2.3 per person, P < .001) than in the seven normal homozygotic subjects (0.14 per person) or in the control group (0.28 per person), whereas the number of lacunes in the white matter was not different among the groups. In conclusion, congenital protein C deficiency may accelerate the progression of silent cerebral infarct formation in hypertension, particularly in the basal ganglia, and may be a potential risk for stroke or vascularly induced dementia.

Interaction of fibrinolysis and prothrombotic risk factors in neonates, infants and children with and without thromboembolism and underlying cardiac disease. a prospective study

To evaluate the role of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) in children with an estimated risk of vascular occlusion reported to range from 7% to 16%, we conducted a prospective study in infants and children with underlying cardiac disease. One hundred and twenty-five children (neonate - 16 years) were investigated. In 9 infants out of the 125 children vascular occlusion occurred, closely related to cardiac catheterisation and arterial or venous lines during major cardiac surgery. Six of the nine neonates and infants with (n=6) and without (n=3) prothrombotic risk factors showed evidence of a basically impaired fibrinolytic system. Five of the nine infants showed increased PAI-1 clearly correlated to the 4G/4G genotype of the plasminogen activator-1 promoter polymorphism along with elevated t-PA concentration before the first diagnostic cardiac catheterisation was performed. One infant presented with increased t-PA concentration only. Five of the six children with reduced fibrinolytic capacity had further prothrombotic risk factors.

CONCLUSION

Data of this study indicate that neonates and infants with underlying cardiac disease and basically increased PAI-1 due to the 4G/4G variant of the PAI-1 promoter polymorphism along with elevated t-PA levels in combination with further prothrombotic risk factors are at high risk of developing early thromboembolism during cardiac catheterisation.

Gene targeting in hemostasis: protein C

Protein C (PC) is the zymogen form of a serine protease, activated protein C (APC), a naturally occurring anticoagulant. In control of the coagulation of blood, APC functions by attenuating thrombin formation. It serves this role through inactivation, by limited proteolysis, of two important cofactors for overall clot formation, one of which, Factor Va (FVa), stimulates prothrombin activation, and another, Factor VIIIa (FVIIIa), enhances activation of coagulation Factor X (FX). In maintaining the fluidity of blood, APC also indirectly functions in fibrinolysis, in one manner by directly inactivating an inhibitor of plasminogen activation, plasminogen activation inhibitor-1 (PAI-1), and in another manner via its role in attenuating thrombin production, with the resulting effect of limiting production of another thrombin-dependent fibrinolytic inhibitor, thrombin activatable fibrinolysis inhibitor (TAFI). PC, and other components of the PC anticoagulant pathway, e.g., protein S (PS), thrombomodulin (Tm), and endothelial cell protein C receptor (EPCR), also can serve as anti-inflammatory mediators, through a number of different thrombin-dependent and thrombin-independent mechanisms. A large number of symptomatic and asymptomatic mutations occur in PC in humans, which express a variety of phenotypes. Generation and characterization of a murine model of a total PC gene inactivation has demonstrated that while an untreated total PC deficiency results in neonatal death through DIC-related abnormalities, a valuable resource is now available to study phenotypes of less severe deficiencies of this protein. Such studies will lead to advances in an understanding of the relative role of this protein system in the various pathways in which it has an influence.

Symptomatic type 1 protein C deficiency caused by a de novo Ser270Leu mutation in the catalytic domain

Heterozygosity for a C8524T transition in the protein C gene converting Ser270(TCG) to Leu(TTG) in the protease domain was identified in a family with venous thrombosis. The mutation was associated with parallel reduction in plasma levels of protein C anticoagulant activity and protein C antigen, which is consistent with a type 1 deficiency. Transient expression of mutant protein C cDNA in human kidney 293 cells and analysis of protein C antigen in culture media and cell lysates showed that the secretion of mutant protein compared with wild-type protein was reduced by at least 97% while the intracellular content of mutant and wild-type protein was similar. Northern blot analysis of total mRNA from transfected cells showed no reduction of the mutant protein C mRNA compared with wild-type protein C mRNA. Collectively, these results indicate that the Ser270Leu mutation in the affected family caused the plasma protein C deficiency and are consistent with a disease mechanism that involves synthesis of mutant protein followed by intracellular degradation before its secretion into the extracellular space. The mutation was not present in the parents of the proband, suggesting a de novo mutation. Non-paternity was excluded after the analysis of three intragenic protein C polymorphisms and six dinucleotide repeat allele sets located in five different chromosomes.