Phenotypic Associations With the HMOX1 GT(n) Repeat in European Populations

Heme oxygenase 1 is a key enzyme in the management of heme in humans. A GT(n) repeat length in the heme oxygenase 1 gene (HMOX1) has been widely associated with a variety of phenotypes, including susceptibility to and outcomes in diabetes, cancer, infections, and neonatal jaundice. However, studies have generally been small and results inconsistent. In this study, we imputed the GT(n) repeat length in participants from 2 UK cohort studies (the UK Biobank study (n = 463,005; recruited in 2006-2010) and the Avon Longitudinal Study of Parents and Children (ALSPAC; n = 937; recruited in 1990-1991)), with the reliability of imputation tested in other cohorts (1000 Genomes Project, Human Genome Diversity Project, and Personal Genome Project UK). Subsequently, we measured the relationship between repeat length and previously identified associations (diabetes, chronic obstructive pulmonary disease, pneumonia, and infection-related mortality in the UK Biobank; neonatal jaundice in ALSPAC) and performed a phenomewide association study in the UK Biobank. Despite high-quality imputation (correlation between true repeat length and imputed repeat length > 0.9 in test cohorts), clinical associations were not identified in either the phenomewide association study or specific association studies. These findings were robust to definitions of repeat length and sensitivity analyses. Despite multiple smaller studies identifying associations across a variety of clinical settings, we could not replicate or identify any relevant phenotypic associations with the HMOX1 GT(n) repeat.

Associations between UGT1A1 and SLCO1B1 polymorphisms and susceptibility to neonatal hyperbilirubinemia in Thai population

Hyperbilirubinemia is the main mechanism that causes neonatal jaundice, and genetics is one of the risk factors of hyperbilirubinemia. Therefore, this study aims to explore the correlation between two genes, UGT1A1 and SLCO1B1, and hyperbilirubinemia in Thai neonates. One hundred thirty seven neonates were recruited from Division of Clinical Chemistry, Ramathibodi Hospital. UGT1A1*28 and *6 were determined by pyrosequencing whereas, SLCO1B1 388A > G and 521 T > C genetic variants were determined by TaqMan® real-time polymerase chain reaction. Neonates carrying with homozygous (AA) and heterozygous (GA) variants in UGT1A1*6 were significantly related to hyperbilirubinemia development compared with wild type (GG; P < 0.001). To the combined of UGT1A1, total bilirubin levels in homozygous variant were higher significantly than heterozygous variant and wild type (P = 0.002, P = 0.003, respectively). Moreover, SLCO1B1 combination was significant differences between the hyperbilirubinemia and the control group (P = 0.041). SLCO1B1 521 T > C variant provide protection for Thai neonatal hyperbilirubinemia (P = 0.041). There are no significant differences in UGT1A1*28 and SLCO1B1 388A > G for the different severity of hyperbilirubinemia. The combined UGT1A1*28 and *6 polymorphism is a strong risk factor for the development of severe hyperbilirubinemia in Thai neonates. Therefore, we suggest neonates with this gene should be closely observed to avoid higher severities of bilirubin.

Upshaw-Schulman Syndrome with a Novel Deletion in Exon 17 of ADAMTS 13 Gene

Upshaw-Schulman syndrome is a rare congenital form of thrombotic thrombocytopenic purpura (TTP) characterized by single or recurrent episodes of thrombocytopenia, microangiopathic hemolyticanemia (MAHA), and widespread microvascular thrombosis, leading to the ischemic damage of multiple organs (mainly kidney, heart and brain). A 6-mo-old female infant, second born of a third-degree consanguineous marriage, with a history of severe neonatal jaundice with thrombocytopenia secondary to hemolysis requiring exchange transfusion on day 2 of life, presented with high-grade fever without focus of 2-d duration. Initial workup revealed microangiopathic hemolyticanemia with thrombocytopenia. In view of microangiopathic hemolyticanemia with thrombocytopenia against a background of severe neonatal jaundice, a diagnosis of congenital TTP was considered and was managed with FFP transfusion. The diagnosis was confirmed with her exome sequencing showing autosomal recessive homozygous frameshift deletion c.2063delG (p.Trp688fs) at Exon 17 (NM_139025) of ADAMTS 13 gene.

Ensemble learning for the early prediction of neonatal jaundice with genetic features

BACKGROUND

Neonatal jaundice may cause severe neurological damage if poorly evaluated and diagnosed when high bilirubin occurs. The study explored how to effectively integrate high-dimensional genetic features into predicting neonatal jaundice.

METHODS

This study recruited 984 neonates from the Suzhou Municipal Central Hospital in China, and applied an ensemble learning approach to enhance the prediction of high-dimensional genetic features and clinical risk factors (CRF) for physiological neonatal jaundice of full-term newborns within 1-week after birth. Further, sigmoid recalibration was applied for validating the reliability of our methods.

RESULTS

The maximum accuracy of prediction reached 79.5% Area Under Curve (AUC) by CRF and could be marginally improved by 3.5% by including genetic variant (GV). Feature importance illustrated that 36 GVs contributed 55.5% in predicting neonatal jaundice in terms of gain from splits. Further analysis revealed that the main contribution of GV was to reduce the false-positive rate, i.e., to increase the specificity in the prediction.

CONCLUSIONS

Our study shed light on the theoretical and practical value of GV in the prediction of neonatal jaundice.

Gene Mutation in Neonatal Jaundice - Mutations in UGT1A1 and OATP2 Genes

This study evaluated the correlation of UGT1A1, OATP2 gene mutations and hyperbilirubinemia in newborns in Northern China. Gene mutations were analyzed at the 211 locus of UGT1A1 (Gly71Arg) and 388 locus of OATP2 (Asn130Asp). The 226 enrolled infants were divided into high, moderate, and low risk subgroups according to American Academy of Pediatrics guideline. Blood samples of the enrolled infants were collected for the analysis of the PCR-restriction fragment length polymorphism. The genotypes and allele frequencies of the polymorphisms were compared in each group. Both UGT1A1 and OATP2 gene mutations occur more often in high risk group and moderate risk group than in low risk group. The results suggested that Gly71Arg and Asn130Asp mutations in UGT1A1 and OATP2 genes might be involved in the development of hyperbilirubinemia in neonates.

Neonatal screening of glucose-6-phosphate dehydrogenase deficiency in Yanbu, Saudi Arabia

Objective: To determine the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in the population tested, and to evaluate the prevalence of neonatal jaundice in newborns with G6PD deficiency.

Methods: Cord blood of all babies born between October 1996 and October 1998 at the Royal Commission Medical Center in Yanbu, Saudi Arabia, was screened for G6PD deficiency by fluorescent spot test. The results of screening of cord blood samples were reported to the physician in charge, and also placed on the files of the babies and their mothers. These babies were observed for 72 h and discharged if no jaundice developed.

Results: During this two-year period, 2505 neonatal cord blood samples from 1278 boys and 1227 girls were screened for G6PD. There were 50 positive results for G6PD deficiency (39 boys and 11 girls), and the prevalence was estimated to be around 2%. The sex-specific prevalence for boys was 3.05%, and for girls 0.9%. Male to female ratio was 3:1. Neonatal jaundice developed in six (12%) babies, five male and one female. All were treated with phototherapy and discharged within one week of birth.

Conclusion: The prevalence of G6PD is relatively high in Yanbu. Routine neonatal screening in areas with a high prevalence of G6PD in Saudi Arabia is justifiable.

[Research progress on the relationship between SLCO1B1 gene and neonatal jaundice]

Organic anion transporter 2 (OATP2) is an uptake transporter located on the basolateral membrane of human hepatocytes. It mediates the transportation of various organic solutes including bilirubin and impacts bilirubin metabolism. It is encoded by the gene of solute carrier organic anion transporter family member 1B1 and the gene variants that inhibit hepatic bilirubin uptake function may reduce the normal functional level of bilirubin elimination and result in neonatal hyperbilirubinemia. In recent years, some studies have indicated that variants of SLCO1B1 are associated with neonatal jaundice. This article reviews the research advance in SLCO1B1 with respect to the structure and function and the relationship between SLCO1B1 mutations and neonatal jaundice.

Bilirubin uridine diphosphate-glucuronosyltransferase variation is a genetic basis of breast milk jaundice

OBJECTIVE

To evaluate the role of bilirubin UDP-glucuronosyltransferase family 1, polypeptide A1 (UGT1A1) gene variations on prolonged unconjugated hyperbilirubinemia associated with breast milk feeding (breast milk jaundice [BMJ]).

STUDY DESIGN

UGT1A1 gene allelic variation was analyzed in 170 Japanese infants with BMJ with polymerase chain reaction-direct sequencing, and their genotypes compared with serum bilirubin concentrations. In 62 of 170 infants, serum bilirubin concentration was followed after 4 months of life. Genotypes were examined in 55 infants without BMJ.

RESULTS

Of 170 infants with BMJ, 88 (51.8%) were homozygous UGT1A1*6. Serum bilirubin concentrations (21.8 ± 3.65 mg/dL) were significantly greater than in infants with other genotypes (P < .0001). The Gilbert UGT1A1*28 allele was not detected in infants with BMJ, except in an infant who was compound heterozygous with UGT1A1*6. At 4 months of age, serum bilirubin concentration improved to >1 mg/dL, except in 2 infants who were homozygous UGT1A1*7. Homozygous UGT1A1*6 was not detected in the control group.

CONCLUSION

One-half of the infants with BMJ were homozygous UGT1A1*6 and exhibited a serum bilirubin concentration significantly greater than other genotypes. This finding indicates that UGT1A1*6 is a major cause of BMJ in infants in East Asia. Previous finding have demonstrated that 5β-pregnane-3α,20β-diol present in breast milk inhibits p.G71R-UGT1A1 bilirubin glucuronidation activity. Thus, prolonged unconjugated hyperbilirubinemia may develop in infants with UGT1A1*6 who are fed breast milk.

Prevalence of uridine glucuronosyl transferase 1A1 (UGT1A1) mutations in Malay neonates with severe jaundice

A number of genetic risk factors have been implicated in the development of neonatal severe hyperbilirubinaemia. This includes mutations in the uridine glucoronosyl transferase 1A1 (UGT1A1) gene which is responsible for unconjugated hyperbilirubinemia in Gilbert's Syndrome. We studied the prevalence of UGT1A1 gene mutations in a group of Malay neonates to determine whether they are risk factors to severe neonatal jaundice. One hundred and twenty-five Malay neonates with severe hyperbilirubinemia were studied. Ninety-eight infants without severe hyperbilirubinaemia were randomly selected from healthy Malay term infants (controls). DNA from EDTA cord blood samples were examined for UGT1A1 mutations nt211G > A and nt247T > C using established Taqman SNP genotyping assays and the UGT1A1*28 variant was detected by the Agilent 2100 bioanalyzer. All samples were also screened for common Malay G6PD variants using established techniques. The frequency of UGT1A1 211G > A mutation is significantly higher in the severely hyperbilirubinemic group (13%) than the control group (4%; p = 0.015) and all the positive cases were heterozygous for the mutation. There was no significant difference in the frequency of UGT1A1*28 mutation between the severely hyperbilirubinemic (3.5%) and the control group (0.01%; p = 0.09). None of the neonates in both groups carried the nt247 T > C mutation. The prevalence of G6PD mutation was significantly higher in the severely jaundiced group than control (9% vs 4%; p = 0.04). In conclusion, nt 211 G > A alleles constitute at least 12% of UGT1A1 mutations underlying unconjugated hyperbilirubinemia and appears to be a significant independent risk factor associated with severe neonatal hyperbilirubinemia in the Malay newborns.

Polymorphic variants of UGT1A1 in neonatal jaundice in southern Brazil

Alterations in the hepatic conjugation of bilirubin due to uridyl-diphosphate-glucuronosyltransferase 1A1 (UGT1A1) polymorphisms have been proposed as risk factors to neonatal jaundice. Herein, we estimated the frequency of genotypes of the promoter region of UGT1A1 gene in newborns and evaluated its association with severe hyperbilirubinemia. Prospective study of cases and controls including all newborns admitted for phototherapy at HCPA, Brazil, during 9 months; 490 babies were enrolled and PCR was performed. Polymorphic genotypes were detected in 16% of the patients and 7 of the 10 possible genotypes were identified with higher prevalence of polymorphisms in Afro-descendants. In this sample, the variants of UGT1A1 were not associated to severe hyperbilirubinemia; other genic factors should be sought in this high miscegenation area of Brazil.

[Relationship between glucose-6-phosphate dehydrogenase gene mutations and neonatal jaundice in Naning, Guangxi]

OBJECTIVE

To study the correlation between glucose-6-phosphate dehydrogenase (G-6-PD) activities and three common mutations of G-6-PD gene G1388A, G1376T and A95G and investigate the effects of G-6-PD gene mutations on neonatal jaundice in Nanning, Guangxi.

METHODS

One hundred and twenty-four neonates from Nanning, Guangxi, with hyperbilirubinemia were enrolled. The ARMS-PCR and PCR/REA methods were used to determine G-6-PD gene mutations. G-6-PD activities were measured using the NBT method. The incidence of acute bilirubin encephalopathy and the peak bilirubin concentration 72 hrs after birth were compared between the neonates with different genotypes and between the G-6-PD mutation and normal groups. The risk of blood serum bilirubin >340 mumol/L was evaluated by logistic regression analysis.

RESULTS

Of the 124 cases, gene mutations were found in 37 cases, including G1388A (n=20), G1376T (n=14), A95G (n=4) and G1388A+A95G (n=1). Five cases (25%) showed normal G-6-PD activities in the G1388A gene mutation group and 4 (29%) had normal G-6-PD activities in the G1376T G1388A gene mutation group. All of 4 cases of A95G G1388A gene mutation showed a deficiency of G-6-PD activities. There were no significant differences in the incidence of acute bilirubin encephalopathy and the peak bilirubin concentration 72 hrs after birth between the G1388A and G1376T G1388A gene mutation groups. The incidence of acute bilirubin encephalopathy, the peak bilirubin concentration 72 hrs after birth and the risk of serum bilirubin >340 micromol/L in the G-6-PD mutation group were not different from the normal group.

CONCLUSIONS

G1388A, G1376T and A95G are common G-6-PD gene mutations in Nanning, Guangxi. The false negative results may be received when the NBT method is used for diagnosis of G-6-PD deficiency. There are similar effects on the incidence of acute bilirubin encephalopathy and the peak bilirubin concentration 72 hrs after birth between different gene mutation groups. G-6-PD gene mutations alone may not contribute to the development of acute bilirubin encephalopathy and the changes of peak bilirubin concentration 72 hrs after birth and the risk of serum bilirubin >340 micromol/L.

Are glutathione S-transferase gene polymorphisms linked to neonatal jaundice?

Glutathione S-transferases (GSTs) are a major group of phase II detoxification enzymes involved in the metabolism of both endogenous and xenobiotic compounds. In addition to their catalytic function in detoxification, GSTs participate in binding to nonsubstrate ligands such as bilirubin. Ligandin, which is one of the principal hepatic-binding proteins, is also a member of the GST family. The aim of the present study was to investigate the possible relationship between neonatal jaundice and the GST gene polymorphisms. The study cohort consisted of a patient group of 116 newborns (plasma bilirubin levels > or = 15 mg/dl) and a control group of 54 newborns (plasma bilirubin levels <13 mg/dl). In the patient group, the null genotype frequencies in GSTM1 and GSTT1 were 52.6 and 19%, respectively; in the control group, these were 63 and 27.8%, respectively. The frequencies of GSTM1 and GSTT1 were similar in the patient and control groups (p > 0.05). Total bilirubin levels were found to be significantly higher in patients with the GSTM1 null genotype than in patients with the GSTM1 wild genotype (p = 0.042). There was no statistically significant difference in total bilirubin levels between patients with the null GSTT1 genotype and those with the wild GSTT1 genotype. It is conceivable that there is a relation between GSTM1 gene polymorphism and total bilirubin levels in neonatal jaundice. We suggest that GSTM1 gene polymorphisms may affect ligandin functions in hepatocytes, which are important in bilirubin transportation. Consequently, patients with the GSTM1 null genotype may have higher total levels of bilirubin.

Neonatal cholestatic jaundice as the first symptom of a mutation in the hepatocyte nuclear factor-1beta gene (HNF-1beta)

This report describes the phenotype of a novel de novo heterozygous frameshift mutation in the hepatocyte nuclear factor-1beta gene (HNF-1beta or TCF2) manifest as a neonatal paucity of intrahepatic bile ducts. HNF-1beta mutations should be considered in neonates with cholestatic jaundice associated with renal malformation or diabetes mellitus.

The frequency of UDP-glucuronosyltransferase 1A1 promoter region (TA)7 polymorphism in newborns and it's relation with jaundice

Increased bilirubin formation and decreased bilirubin conjugation play an important role in the pathogenesis of the newborn jaundice. Although physiologic jaundice is seen in most of the newborns, there are many risk factors that affect the severity and duration of hyperbilirubinemia. The latest studies showed that the frequency and severity of neonatal jaundice have been increased when mutations of the gene coding UDP-glucuronosyltransferase(UGT)1A1 coexist with other risk factors. Healthy term newborns weighing over 2500 g. were included in this study. The patient group consisted of 107 newborns either with total bilirubin level over 15 mg dl(-1) within 7 days or 5 mg dl(-1) after 15 days of age. The control group consisted of 55 newborns with bilirubin levels in physiological ranges. We investigated the frequency of promoter region [thymine-adenine(TA)]7 polymorphism in UGT1A1 gene. Factors which might cause pathologic and prolonged jaundice with coexisting polymorphism were also investigated. UGT1A1 6/7 genotype was found to be 11% in patient group and 13% in the control group. The difference between patient and control groups was not statistically significant. (TA)7 allele frequency was 0.069 and it is concluded that UGT1A1 promoter region polymorphism was not a risk factor for neonatal jaundice.

Molecular basis of glutathione reductase deficiency in human blood cells

Hereditary glutathione reductase (GR) deficiency was found in only 2 cases when testing more than 15 000 blood samples. We have investigated the blood cells of 2 patients (1a and 1b) in a previously described family suffering from favism and cataract and of a novel patient (2) presenting with severe neonatal jaundice. Red blood cells and leukocytes of the patients in family 1 did not contain any GR activity, and the GR protein was undetectable by Western blotting. Owing to a 2246-bp deletion in the patients' DNA, translated GR is expected to lack almost the complete dimerization domain, which results in unstable and inactive enzyme. The red blood cells from patient 2 did not exhibit GR activity either, but the patient's leukocytes contained some residual activity that correlated with a weak protein expression. Patient 2 was found to be a compound heterozygote, with a premature stop codon on one allele and a substitution of glycine 330, a highly conserved residue in the superfamily of NAD(P)H-dependent disulfide reductases, into alanine on the other allele. Studies on recombinant GR G330A revealed a drastically impaired thermostability of the protein. This is the first identification of mutations in the GR gene causing clinical GR deficiency.

Neonatal Jaundice and Bilirubin UDP-Glucuronosyl Transferase 1A1 Gene Polymorphism in Turkish Patients

Bilirubin uridine diphosphate-glucuronosyltransferase (B-UGT) is the rate-limiting enzyme for the conjugation of bilirubin with glucuronic acid in its excretion process into the bile. Variations in B-UGT gene (UGT-1A1) have been related to disorders characterised by hyperbilirubinaemia. The aim of this study was to investigate whether the number of thymine-adenine repeats in the promoter region of UGT-1A1 was related to non-physiologic hyperbilirubinemia of unexplained aetiology in Turkish newborns. These patients (n=106) were genotyped for their thymine-adenine repeat number in the promoter region of UGT-1A1, and were divided into two groups according to their bilirubin level. Forty-nine newborns with bilirubin levels higher than 17 mg/dl within the first ten days of life comprised the hyperbilirubinaemia group and 25 newborns with bilirubin levels higher than 10 mg/dl after fifteen days of life formed the prolonged jaundice group. Thirty-two newborns were included as healthy controls. The observed frequencies for the wild-type six repeat allele thymine-adenine (TA(6)) within each subject group were similar (P>0.05; 75.5%, 78.0% and 73.4%, respectively). Likewise, the distribution of TA(6/6), TA(6/7) and TA(7/7) genotypes among three groups were similar. These results imply that the TA(7) repeat allele of UGT1A1 (UGT1A1*28) is a common variant in the Turkish population. Our results do not suggest an association between thymine-adenine repeat polymorphism of UGT1A1 and hyperbilirubinaemia of unexplained aetiology or prolonged jaundice in Turkish neonates.

The effect of blue light exposure on the expression of circadian genes: bmal1 and cryptochrome 1 in peripheral blood mononuclear cells of jaundiced neonates

The purpose of this study was to investigate the effect of blue light phototherapy on the expression of circadian genes in peripheral blood mononuclear cells (PBMC) and plasma melatonin levels in neonates. Real-time reverse-transcriptase polymerase chain reaction (RT-PCR) was used to determine the expression of Bmal1 and Cry1 in PBMC, and an enzyme-linked immunosorbent assay was used to determine plasma melatonin levels in 32 breast-milk jaundiced neonates before and after phototherapy, compared with 29 control neonates. The results showed that the expression of Bmal1 was decreased and Cry1 increased significantly after phototherapy. Plasma melatonin levels were decreased after phototherapy. There was no statistical difference in Bmal1 and Cry1 gene expression and plasma melatonin levels in the control group. In conclusion, phototherapy does affect the expression of the circadian genes Bmal1 and Cry1 in PBMC and plasma melatonin concentration in jaundiced neonates. Our results suggest that phototherapy should be timed according to circadian rhythms when treating jaundiced neonates.

The role of UGT1A1*28 mutation in jaundiced infants with hypertrophic pyloric stenosis

Hypertrophic pyloric stenosis (HPS) may be accompanied by jaundice, a condition referred to as the icteropyloric syndrome (IPS). It has long been suspected that the etiology of IPS is an early manifestation of Gilbert's syndrome (GS). Clinical features common to both GS and IPS include jaundice precipitated by fasting and improved with feeding. Prevalence of jaundice in HPS is similar to that of clinically apparent GS in the general population. Discovery of a mutation in the promoter region of the bilirubin uridine diphosphate glucuronosyl transferase gene (UGT1A1*28) as the most common cause of GS has provided a tool to determine the role of GS in IPS. The aims of this study were to determine 1) the prevalence of IPS in a large group of infants with HPS, 2) whether disease severity contributed to the manifestation of IPS, and 3) whether GS played a role in IPS. Radioactive PCR and sequencing were used to determine the presence of UGT1A1*28 mutations. We determined a prevalence of IPS of 14.3% in HPS. Infants with IPS had significantly higher levels of alkalosis than infants with HPS alone. GS mutations were 4-fold higher in IPS (43.8%) than HPS (10.7%). In conclusion, the frequency of jaundice in HPS is similar to that of clinically apparent GS in the general population. Manifestation of IPS results from a more severe degree of metabolic disturbance and the presence of GS mutations.

Neonatal Anemia Associated with Southeast Asian Ovalocytosis

The purposes of this study were to evaluate the reliability of the previously described diagnostic criteria for Southeast Asian ovalocytosis (SAO) in adults in the diagnosis of SAO in newborns and to describe the role of SAO in newborn infants presenting with pallor and jaundice. The inclusion criteria in this retrospective descriptive study were that the patient be a newborn with pallor or jaundice and with ovalocytes in the peripheral blood smear (PBS). The exclusion criteria were newborn status with other causes of neonatal hemolysis or anemia. Controls were age-matched newborn infants who did not have SAO or other causes of neonatal anemia or hemolysis. Hematological data were assessed with a hematology analyzer. DNA analysis for SAO band 3 was done by polymerase chain reaction. Among 107 newborn infants with SAO, 30 infants were excluded from the study. The exclusions were premature infants, an infant with congenital syphilis, low-birth-weight infants, infants with ABO blood group incompatibility, infants with 3-thalassemia, infants with hemoglobin E heterozygote or homozygotes, glucose-6-phosphate dehydrogenase-deficient infants, and infants with fetomaternal hemorrhage. The DNA analysis for SAO band 3 was done in 56 newborns, and 54 had positive results for SAO band 3 gene deletion. Approximately one half of the 54 newborn infants with SAO had hyperbilirubinemia, and 3 had severe hyperbilirubinemia. The mean hemoglobin concentration, packed cell volume, and red blood cell (RBC) count in the infants with SAO in the first week of life were significantly lower than those in control infants. The mean absolute number of reticulocytes, mean corpuscular hemoglobin, and red cell volume distribution width in infants with SAO band 3 in the first week of life were significantly higher than those in control infants. The neonatal diagnosis of SAO can be made by examination of RBC morphology in the PBS with the presence of stomatocytes, theta cells, and > or = 25% ovalocytes. SAO plays a role in anemia and hyperbilirubinemia in newborn infants.

[Role of genetic factors in occurrence of neonatal jaundice in Guangxi region]

OBJECTIVE

To investigate the possible role of the UGT1A1 G71R or the OATP2 A388G genes mutation with coexisting G-6-PD deficiency in occurrence of neonatal hyperbilirubinemia.

METHODS

Totally 109 umbilical cord blood samples were collected for the screening of G-6-PD activity by nitroblue tetrazolium (NBT) test and identification of G71R gene type by polymerase chain reaction combined with allele-specific oligonucleotide assay (ASO-PCR). At the same time, for 101 of the 109 cord blood samples A388G gene types were tested by restriction fragment length polymorphism (RFLP). According to G-6-PD activity and G71R or A388G genotype, the neonates were allocated into different groups. The authors compared the incidence rate of hyperbilirubinemia among different groups. Ten samples were sequenced to validate the results.

RESULTS

Among the 109 umbilical cord blood specimens, the allele frequency of G71R was 22.03% in G-6-PD deficient group, 28.0% in G-6-PD normal group. The incidence rate of neonatal hyperbilirubinemia for those neonates who were G-6-PD deficient with coexisting homozygous or heterozygous variant of the G71R gene was significantly higher than that of neonates who were G-6-PD normal and had wild type G71R gene type, chi(2) = 10.45, P = 0.0012. The odds ratio (OR) of the former was 18.00 (95% CI: 2.12, 152.9). Among the 101 neonates, the allele frequency of A388G was 20.0% in G-6-PD deficient group and 18.5% in G-6-PD normal group. The incidence rate of neonatal hyperbilirubinemia for those neonates who were G-6-PD deficient with coexisting homozygous or heterozygous variant of the A388G gene was significantly higher than that of the neonates who were G-6-PD normal and had wild type A388G gene type, chi(2) = 10.39, P = 0.0013. The OR of the former was 11.8 (95% CI: 2.15, 56.48).

CONCLUSION

G-6-PD deficiency coexists with G71R or A388G mutation in some individuals in Guangxi region. UGT1A1 G71R gene mutation combined with G-6-PD deficiency or A388G gene mutation combined with G-6-PD deficiency may play a coordinative role in the development of neonatal hyperbilirubinemia.

Molecular heterogeneity of glucose-6-phosphate dehydrogenase (G6PD) variants in the south of Thailand and identification of a novel variant (G6PD Songklanagarind)

Two hundred and twenty-five G6PD-deficient subjects in Songklanagarind Hospital in the south of Thailand comprising 210 males and 15 females were studied. Neonatal jaundice was detected in 85% of these patients. Acute hemolysis related to infection was detected in 17.3% of the G6PD-deficient subjects. Drug-induced acute hemolysis was detected in 1.8% and favism was observed in 3.6% of G6PD-deficient patients. The molecular analysis was performed on 134 G6PD-deficient individuals by a combination of PCR-RFLP, multiplex polymerase chain reaction by multiple tandem forward primers and a common reverse primer assay (MPTP) and DNA sequencing to characterize the mutations of the samples with abnormal MPTP bands. We found 10 different missense G6PD mutations and the three most common variants were G6PD Viangchan 871,G-->A (31.3%), G6PD Kaiping 1388,G-->A (20.1%) and G6PD Mahidol 487,G-->A (17.2%) followed by G6PD Canton 1376,G-->T (9.7%), G6PD Union 1360,C-->T (2.2%), G6PD Gaohe 95,A-->G (1.5%), G6PD Quing Yuan 392,G-->T (0.7%), G6PD Mediterranean 563,C-->T (0.7%), G6PD Songklanagarind 196,T-->A (0.7%), silent mutation 1311,C-->T (6.7%), and uncharacterized variant (9%). A novel missense mutation at codon 196, TTC-->ATC in exon 4 of the G6PD gene predicting a single amino acid substitution, Phe66Ile was identified and we designated this novel class II variant as G6PD Songklanagarind. The G6PD variants among the Thais in the southern part are heterogeneous and G6PD Viangchan, Kaiping, Mahidol, and Canton variants account for about 78% of the cases. Our findings provide some evidence that G6PD Viangchan and Mahidol are common Southeast Asian variants and support the theory of genetic drifts throughout Southeast Asia.

Vigintiphobia revisited

In this review the historical tenets and evidence-based clinical research in support of a bilirubin exchange threshold of >20 mg/dL for the healthy term neonate are revisited. In addition, a hypothesis is ventured that recent cases of kernicterus are related in part to changes in population factors coupled with genetic predispositions that have unmasked an unappreciated potential for marked neonatal hyperbilirubinemia.

Neonatal hyperbilirubinemia and the bilirubin uridine diphosphate-glucuronosyltransferase gene: the common -3263T > G mutation of phenobarbital response enhancer module is not associated with the neonatal hyperbilirubinemia in Japanese

BACKGROUND

Neonatal hyperbilirubinemia is frequent and severe in Japanese newborns. Previously, it has been reported that half of the Japanese neonates with severe hyperbilirubinemia carried the 211G > A (p.G71R) mutation of the bilirubin uridine diphosphate-glucuronosyltransferase (UGT1A1) gene causing Gilbert syndrome. Recently, it was reported that the -3263T > G mutation in the phenobarbital response enhancer module in UGT1A1 was associated with the majority of cases of Gilbert syndrome. The gene frequency of the -3263T > G mutation was determined and the relation with neonatal hyperbilirubinemia in Japanese was studied.

METHODS

UGT1A1 in 119 neonates born at Yamagata University Hospital, Yamagata, Japan, and 26 subjects who had undergone phototherapy due to severe hyperbilirubinemia at four other hospitals were studied. The gene frequency of -3263T > G mutation in Japanese, Korean, Chinese and German healthy adult controls was also determined. Hyperbilirubinemia was assessed with a Jaundice Meter and UGT1A1 was analyzed by sequence determination or restriction enzyme method.

RESULTS

The gene frequency of the -3263T > G mutation was 0.26 in Japanese subjects and was similar to the prevalence in Korean, Chinese and German populations. However, there was no significant increase in the gene frequency of the mutation in the neonates who required phototherapy for hyperbilirubinemia compared to that in the neonates without severe hyperbilirubinemia. In addition, neonates with or without the mutation did not show a significant change in the level of bilirubin and the mutation also did not show a synergic effect with the 211G > A mutation on the level of bilirubin.

CONCLUSION

The -3263T > G mutation is not likely to be associated with the neonatal hyperbilirubinemia in Japanese.

Risk factors for severe hyperbilirubinemia in neonates

The incidence of severe neonatal hyperbilirubinemia is higher in Asians than in whites. A case-control study was designed to investigate the effects of eight known risk factors [breast feeding, ABO incompatibility, premature birth, infection, cephalohematoma, asphyxia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and variant UDP-glucuronosyltransferase 1A1 (UGT1A1) gene] and a suspicious analog [organic anion transporter 2 (OATP 2) gene] on severe hyperbilirubinemia in Taiwanese neonates. The 72 study subjects and 100 hospital control subjects consisted of neonates with peak serum bilirubin levels > or =342 microM and <256.5 microM, respectively. The PCR-restriction fragment length polymorphism method was applied to detect the UGT1A1, OATP 2, and G6PD genes. The results of multivariate logistic regressions, adjusted for covariates, revealed odds ratios (ORs) of 4.64 [95% confidence interval (CI): 2.25-9.57; p < 0.001], 3.36 (95% CI: 1.54-7.35; p=0.002), and 3.02 (95% CI: 1.30-6.99; p=0.010) for neonates who were fed with breast milk, and carry the variant UGT1A1 gene at nucleotide 211 and the variant OATP 2 gene at nucleotide 388, respectively. The ORs, adjusted for covariates, for the other six risk factors were not statistically significant. The ORs in neonates who had one, two, and three significant risk factors were 8.46 (95% CI: 2.75-34.48; p < 0.001), 22.0 (95% CI: 5.50-88.0; p < 0.001), and 88.0 (95% CI: 12.50-642.50; p < 0.001), respectively. In conclusion, neonates who carry the 211 and 388 variants in the UGT1A1 and OATP 2 genes, respectively, as well as feed with breast milk are at high risk to develop severe hyperbilirubinemia.

Screening for G71R mutation of the UGT1A1 gene in the Javanese-Indonesian and Malay-Malaysian populations

BACKGROUND

There are significant differences in the prevalence and severity of neonatal jaundice among various populations. Recently, it has been reported that a mutation of the UGT1A1 gene, glycine to arginine at codon 71 (G71R), is related to the development of neonatal jaundice in East Asian populations. However, whether the G71R mutation contributes to the high incidence of neonatal jaundice in different Asian populations remains unknown. The authors screened for this mutation in the Javanese-Indonesian and Malay-Malaysian populations.

METHODS

One hundred and thirty-six subjects were enrolled in this study: 68 Javanese-Indonesian adults and 68 Malay-Malaysian newborns (32 with jaundice and 36 without jaundice). Denaturing high-performance liquid chromatography (DHPLC) was used to screen for the G71R mutation, and the results were confirmed by nucleotide sequencing analysis.

RESULTS

With DHPLC, the authors easily and clearly detected seven subjects carrying the G71R mutation: two Javanese-Indonesian adults and five Malay-Malaysian newborns. In the 68 Javanese-Indonesian adults, the genotype distribution for G71R mutation was 66 G/G, two G/R and no R/R genotypes, and the mutated allele frequency was 0.015. In the 68 Malay-Malaysian newborns, genotype distribution for the mutation was 63 G/G, five G/R and no R/R genotypes, and the mutated allele frequency was 0.037. The genotype distributions did not differ significantly between the newborns with jaundice and those without jaundice.

CONCLUSION

The G71R mutation is present, but very rare, in Javanese-Indonesians and Malay-Malaysians. Thus, G71R mutation may not contribute to the high incidence of the neonatal jaundice in South-east Asian populations. DHPLC analysis is a very useful method for detecting the G71R mutation.

[Neonatal screening of glucose-6-phosphate dehydrogenase deficiency in umbilical cord blood]

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most frequent enzyme deficiency. It is a sex-linked genetic disease concerning mostly african, mediterranean and far-eastern populations. The main clinical expression is a hemolytic anemia which can be acute or chronic. During the neonatal period the disease may manifest as neonatal jaundice. We have been asked by the neonate department to set up a blood screening test for this deficiency. We have therefore developed a test using umbilical cord blood. The assay of G6PD has been automatised and red blood cell aspartate-amino-transferase (ASAT) chosen as a reference enzyme to evaluate the age of red blood cells. Normal values of G6PD, ASAT and G6PD/ASAT ratio have been calculated from 235 cord samples. Genetic frequency of this deficiency in 2002 was 6% in male and 1% in female newborns.

Analyses of polymorphism for UGT1*1 exon 1 promoter in neonates with pathologic and prolonged jaundice

In this study, we investigated whether a TATA box polymorphism in the promoter of the UGT1*1 exon I, the most common detected DNA polymorphism in Gilbert's syndrome, is a contributory factor in unexplained pathologic or prolonged jaundice. 38 neonates who had unexplained pathologic jaundice, 37 neonates who had unexplained prolonged jaundice, and 35 healthy, nonjaundiced neonates were enrolled in the study. Genotypes were assigned as follows: 6/6 (homozygous for a normal allele bearing the sequence [TA](6)TAA), 7/7 (homozygous for an abnormal allele with the sequence [TA](7)TAA), and 6/7 (heterozygous with one of each allele). Of the 110 infants, 10 (9%) had 7/7, 51 (46%) had 6/7, and 49 (45%) had 6/6 genotype; the differences between the three groups were not statistically significant. Also no differences were observed among different genotypes and mean serum total bilirubin concentrations. In conclusion, we showed that TA 7/7 and TA 6/7 genotypes are not rare in our population and that the presence of these polymorphisms alone does not play a significant role in the etiology of unexplained pathologic or prolonged neonatal hyperbilirubinemia.

Molecular characterization of ADAMTS13 gene mutations in Japanese patients with Upshaw-Schulman syndrome

We report here 7 new mutations in the ADAMTS13 gene responsible for Upshaw-Schulman syndrome (USS), a catastrophic phenotype of congenital thrombotic thrombocytopenic purpura, by analyzing 5 Japanese families. There were 3 mutations that occurred at exon-intron boundaries: 414+1G>A at intron 4, 686+1G>A at intron 6, and 1244+2T>G at intron 10 (numbered from the A of the initiation Met codon), and we confirmed that 2 of these mutations produced aberrantly spliced messenger RNAs (mRNAs). The remaining 4 mutations were missense mutations: R193W, I673F, C908Y, and R1123C. In expression experiments using HeLa cells, all mutants showed no or a marginal secretion of ADAMTS13. Taken together with the findings in our recent report we determined the responsible mutations in a total of 7 Japanese patients with USS with a uniform clinical picture of severe neonatal hyperbilirubinemia, and in their family members, based on ADAMTS13 gene analysis. Of these patients, 2 were homozygotes and 5 were compound heterozygotes. The parents of one homozygote were related (cousins), while those of the other were not. Molecular models of the metalloprotease, fifth domain of thrombospondin 1 (Tsp1-5), and Tsp1-8 domains of ADAMTS13 suggest that the missense mutations could cause structural defects in the mutants.

Difference in plasma bilirubin concentration between monozygotic and dizygotic newborn twins

AIM

To investigate whether inherited factors, other than those already known, influence the bilirubin concentration in neonates of northern European descent, by comparison of monozygotic and dizygotic twins with respect to differences in the plasma bilirubin concentrations between the twins.

METHODS

77 healthy pairs of twins of the same gender with a gestational age > or = 250 d and of northern European descent were included. Fourth postnatal day blood sampling was done. A multiple linear regression analysis was carried out with the difference in serum bilirubin concentration between the twins as the independent factor, and zygosity, gender, gestational age, postnatal age, maternal smoking, ABO blood-type incompatibility, and the differences between the twins in blood haemoglobin concentration, formula feeding and weight loss as dependent factors.

RESULTS

27 pairs of twins were monozygotic and 50 pairs dizygotic. The analysis showed that the difference in serum bilirubin concentration between the twins was dependent on whether the twins were monozygotic or dizygotic, i.e. the estimated difference in serum bilirubin concentration between the monozygotic twins was 17.8 micromol l(-1) [SE 6.6 micromol l(-1), p = 0.02, 95% confidence interval (95% CI) 3.4, 32.3 micromol l(-1)] less than the difference between the dizygotic twins, adjusted for the above-mentioned potential confounders. The difference in serum bilirubin concentration between the twins was positively correlated to the difference in weight loss (%) between the twins (adjusted estimate 5.2 micromol l(-1), SE 2.1 micromol l(-1) , p = 0.01, 95% CI 1.2, 9.3 micromol l(-1)).

CONCLUSION

In a population of northern European descent, other genetic factors than gender and ABO blood type were significant for the plasma bilirubin concentration in healthy infants.

[Glucose-6-phosphate dehydrogenase deficiency, neonatal hyperbilirubinemia and Gilbert syndrome]

The aim of this work was to evaluate the influence of abnormal UDP-glucoronosyltransferase-1 (UGT1A1) gene variant, on the incidence and severity of neonatal hyperbilirubinemia, in glucose-6-phosphate dehydrogenase (G6PD) deficient newborns. The A(TA)nTAA region in the promoter of the UGT1A1 gene was analysed in 20 children with G6PD deficiency. Fourteen of these children had the African type variant (G6PDA-) and 6 had different variants (G6PDNara, G6PDGuadalajara, G6PDDurham, G6PDTomah, G6PDAveiro e G6PDNashville) related to chronic nonspherocytic haemolytic anaemia (CNSHA). The existence of a positive history of neonatal hyperbilirubinemia, as well as its severity was registered. The incidence of neonatal hyperbilirubinemia was increased in this group of children (90%) and was not associated with abnormal alleles of the UGT1A1 gene. It was not possible to assess the influence of abnormal alleles in the severity of the neonatal hyperbilirubinemia. However, these abnormal alleles did not account for the severity of jaundice in children who presented variants related to CNSHA, since 5 were treated with an exchange transfusion and none presented abnormal alleles.

Relationship between bilirubin UDP-glucuronosyl transferase 1A1 gene and neonatal hyperbilirubinemia

The variation rate within the coding region of UDP-glucuronosyl transferase 1A1 (UGT1A1) gene in Taiwan Chinese was found to be 29.3%. This study sought to determine whether that high variation rate of UGT1A1 gene is a risk factor for neonatal hyperbilirubinemia. The study subjects consisted of 123 newborn infants suffering from unconjugated hyperbilirubinemia who had no known risk factors for hyperbilirubinemia and 218 healthy control neonates. The promoter area, exons 1 to 4, coding region of exon 5, and the flanking intronic regions in UGT1A1 gene were determined by the PCR in all subjects. Wild UGT1A1 gene, variation in the promoter, variation at nucleotide 211, variation at nucleotide 1091, and compound heterozygous variation of UGT1A1 gene were found. The percentage of neonates with wild UGT1A1 gene and the percentage of neonates with variation at nucleotide 211 were significantly different between the study subjects and controls. The percentages with bilirubin >or=342 micro M (20.0 mg/dL) and with persistent hyperbilirubinemia in the subjects carrying homozygous variation at nucleotide 211 (Gly71Arg) were significantly higher than the neonates carrying wild type or other genotypes. In conclusion, this study has demonstrated that variation at nucleotide 211 of the UGT1A1 gene is a risk factor for the development of neonatal hyperbilirubinemia. Pediatricians should closely follow hyperbilirubinemic newborn infants who carry homozygous 211 G to A variation in UGT1A1 gene.

Changes in calcium-binding protein expression in the auditory brainstem nuclei of the jaundiced Gunn rat

Sensorineural hearing loss and auditory dysfunction are major sequelae of neonatal hyperbilirubinemia. The sites and cellular effects of bilirubin toxicity in the auditory brainstem pathway are not easily detected. Since altered intracellular calcium homeostasis may play a role in neuronal cell death, we hypothesized that the expression of calcium-binding proteins may be altered in the classic animal model of bilirubin neurotoxicity. The expression of the calcium-binding proteins, calbindin-D28k and parvalbumin, in the brainstem auditory pathway of homozygous recessive jaundiced (jj) Gunn rats was examined by light and electron microscopic immunohistochemistry at 18 days postnatally and compared to the findings obtained from age-matched non-jaundiced heterozygous (Nj) littermate control rats. Immunoreactive staining for both calbindin and parvalbumin was reduced in the cochlear nuclei and the superior olivary complex in jj rats. The extent of the reduction in immunoreactivity was related to the severity of the clinical symptoms. By contrast, immunoreactive staining in other brainstem areas (e.g., dorsal and ventral nuclei of the lateral lemniscus, inferior colliculus), thalamic (medial geniculate body) auditory areas, and neighboring non-auditory structures was similar in jaundiced and control rats. Calbindin-immunoreactive staining in the superior paraolivary and medial superior olivary nuclei in Nj rats was associated with myelinated axons, whereas parvalbumin-immunoreactive staining was localized postsynaptically in neuronal somata and dendrites. Immunoreactive staining for the calcium-binding proteins calbindin and parvalbumin in lower brainstem auditory nuclei shows abnormalities in areas susceptible to the effects of hyperbilirubinemia and provides a sensitive new way to assess bilirubin toxicity in the auditory system.

Cerebellar symptoms heralding bilirubin encephalopathy in Crigler-Najjar syndrome

Children with Crigler-Najjar syndrome type I are at increased risk for neurologic deficits. Cerebellar symptoms are not prominent and appear in adolescent or adult patients with this syndrome. We report a 2-year-old female with Crigler-Najjar syndrome type I who presented severe cerebellar symptoms revealing bilirubin encephalopathy. The patient improved slowly with the duration of phototherapy. Cerebellar symptoms can be the initial manifestation of kernicterus in children with Crigler-Najjar syndrome type I.

Gly71Arg mutation of the bilirubin UDP-glucuronosyltransferase 1A1 gene is associated with neonatal hyperbilirubinemia in the Japanese population

The serum bilirubin level of Japanese newborn infants in their first few days is significantly higher than that in Caucasian newborn infants, suggesting that there might be genetic risk factors for the development of neonatal hyperbilirubinemia in the Japanese population. Recently, it has been reported that a variant TATA box in the promoter region of the bilirubin UDP-glucuronosyltransferase 1 (UGT1A1) gene is associated with the development of neonatal hyperbilirubinemia. This finding led us to the idea that a mutation, glycine to arginine at codon 71 (G71R), in the coding region of the UGT1A1 gene can cause neonatal hyperbilirubinemia. In this study, we determined the genotypic distribution of the G71R mutation in 72 Japanese newborn infants: 23 infants with hyperbilirubinemia and 49 infants without hyperbilirubinemia. In the hyperbilirubinemia group, 15 of 23 newborn infants had the G71R mutation (3 homozygotes and 12 heterozygotes), whereas in the non-hyperbilirubinemia group 16 of 49 newborn infants had the G71R mutation (1 homozygote and 15 heterozygotes). Therefore, the G71R mutation was present significantly more frequently in the hyperbilirubinemia group than in the non-hyperbilirubinemia group. This finding strongly suggests that the presence of the G71R mutation contributes to the development of neonatal hyperbilirubinemia in the Japanese population.

Glucose-6-phosphate dehydrogenase deficiency, the UDP-glucuronosyl transferase 1A1 gene, and neonatal hyperbilirubinemia

BACKGROUND & AIMS

Coinheritance of the A(TA)7TAA promoter variant in the uridine 5'-diphosphate-glucuronosyl transferase 1A1 (UGT1A1) gene and glucose-6-phosphate dehydrogenase (G6PD) deficiency is crucial to hyperbilirubinemia in white male neonates. A variation rate of 29.3% was determined within the coding region of the UGT1A1 gene in Taiwanese subjects, suggesting the hypothesis that this variation may influence incidence of hyperbilirubinemia in male neonates with G6PD deficiency.

METHODS

The full sequence of the UGT1A1 gene was identified for 212 G6PD-deficient and 232 control male neonates by using polymerase chain reaction (PCR).

RESULTS

Both study and control groups were divided into 5 subgroups according to their UGT1A1 genotypes. Most subjects carried G to A variation at nucleotide 211 for both genotypes of heterozygous variation within coding region and homozygous variation. No significant differences were noted for the frequencies of the 5 UGT1A1 genotypes, gestation age, and birth weight comparing the G6PD-deficient and control groups. The incidence of hyperbilirubinemia, however, was significantly higher for the study group than for the controls. This difference was noted only for the subgroup bearing the homozygous variant of the UGT1A1 gene. In the subgroup of homozygous variation, the serum bilirubin value was significantly higher for G6PD-deficient neonates than for controls. All 11 G6PD-deficient neonates with the homozygous 211 G to A variation suffered from hyperbilirubinemia.

CONCLUSIONS

The results indicate that carriage of the homozygous 211 G to A variation within the coding region in the UGT1A1 gene is an additive risk factor for neonatal hyperbilirubinemia in G6PD-deficient Taiwanese male neonates.

Molecular basis of haemoglobinopathies and G6PD deficiency in the Comorian population

INTRODUCTION

The Comoro archipelago is characterised by a high prevalence of red cell genetic disorders such as G6PD deficiency and haemoglobinopathies, being a region endemic for malaria. Over the last 15 years, the city of Marseilles in France has become the main destination for Comorian immigrants. This Comorian community includes patients with sickle cell disease, sickle cell/beta-thalassaemia trait, thalassaemias and G6PD deficiency.

MATERIALS AND METHODS

Allele frequencies for haemoglobin S, beta-thalassaemia and G6PD deficiency were determined from neonatal and prenatal screenings of the Comorian community. Haemoglobin fractions were detected by isoelectrofocalisation, and the quantitation of HbS, HbA, HbA(2) and HbF was performed by cation exchange high performance liquid chromatography. The molecular study involved 31 alleles carrying the betaS mutation (Cd 6 [A-->T]), six beta-thalassaemic alleles and 17 G6PD-deficient alleles, selected from a group of carriers or affected subjects.

RESULTS

Allele frequencies were 3% for haemoglobin S, 1% for beta-thalassaemia trait and 9.5% for G6PD deficiency. Molecular analysis had revealed that the African alleles are predominant, being present in almost all the subjects studied. Mediterranean alleles were found for all the beta-thalassaemia mutations and for three G6PD chromosomes out of 17.

CONCLUSION

These data are consistent with the mixed Arab and African origin of the population of the Comoro Islands, and are of clinical interest in prenatal and newborn screening plans.

Understanding neonatal hyperbilirubinaemia in the era of genomics

The genomics revolution offers novel approaches to scientific investigation. Application of genomics technologies including microarray gene chips will provide a more complete picture of biological phenomena and help define the genetic contribution to disease by monitoring changes in expression across thousands of genes in physiological and clinical contexts. We briefly summarize identified genetic components that contribute to the genesis of neonatal hyperbilirubinaemia with a focus on inborn errors of hepatic bilirubin conjugation and discuss the potential use of microarray gene expression profiling technology to enhance our understanding of the pathogenesis of hyperbilirubinaemic neuronal cell injury. Expanded study using the tools of genomics will shed insights into the genetics of newborn jaundice and the pathogenesis of hyperbilirubinaemic encephalopathy.

[Interest in the study of genetic variants of the promoter region of the UGT1A1 gene in neonatal jaundice]

BACKGROUND

A relationship between polymorphism in the promoter region of the UGT1A1 gene (associated with Gilbert's syndrome) and the development of jaundice has recently been demonstrated. This polymorphism is due to (TA)7 instead of wild-type (TA)6.

OBJECTIVE

To investigate the relationship between Gilbert's syndrome and neonatal jaundice by evaluating the distribution of (TA)7 in a population of newborns.

METHODS

A total of 136 newborns were studied: 21 had neonatal jaundice, 69 were healthy and the remaining newborns had various diseases. DNA from each patient was used to amplify, by polymerase chain reaction, the promoter region of the UGT1A1 gene, which flanks the TATA box where the polymorphism is located.

RESULTS

In the group without jaundice, 53 % of the newborns were normal (6/6 genotype), 40 % were 6/7 and 7 % were 7/7. In the group with jaundice, 33 % of the newborns were normal, 53 % were heterozygous (6/7) and 14 % were homozygous (7/7). Comparison of the groups revealed that the prevalence of UGTA1A polymorphism tended to be greater among jaundiced newborns (p 0.09).

CONCLUSION

The results of this study suggest that there is a relationship between neonatal jaundice and Gilbert's syndrome among the Spanish population. These results, together with those of other authors, suggest that genetic screening for Gilbert's syndrome should be included in the investigation of neonatal jaundice in our population. Further studies with a greater number of subjects would determine the exact relationship between marked neonatal jaundice and IGTA1A polymorphism. Key words:

Glucose-6-phosphate dehydrogenase (G6PD) mutations in Thailand: G6PD Viangchan (871G>A) is the most common deficiency variant in the Thai population

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common hereditary disorder in humans. Through a population study for G6PD deficiency using a cord blood quantitative G6PD assay in Bangkok, Thailand, we found that the prevalence of G6PD deficiency is 11.1% in Thai male (N=350) and 5.8% in female (N=172) cord blood samples. Among the neonates with hyperbilirubinemia, the prevalence of G6PD deficiency is 22.1% in males (N=140) and 10.1% in females (N=89). We developed a PCR-restriction enzyme-based method to identify G6PD Viangchan (871G>A), and searched for this and 9 other mutations in DNA from G6PD deficient blood samples. G6PD Viangchan (871G>A) was the most common mutation identified (54%), followed by G6PD Canton (1376G>T; 10%), G6PD Mahidol (487G>A; 8%), G6PD Kaiping (1388G>A; 5%), G6PD Union (1360C>T; 2.6%) and "Chinese-5" (1024C>T; 2.6%). Among 20 neonates with hyperbilirubinemia, G6PD Viangchan was also most frequently identified (60%), followed by G6PD Canton (10%), G6PD Mahidol, G6PD Union, and G6PD Kaiping (5% each). G6PD Viangchan appears from this study to be the most common G6PD mutation in the Thai population, bringing into question previous reports that G6PD Mahidol is most prevalent. G6PD Viangchan, together with G6PD Mahidol and G6PD Canton, are responsible for over 70% of G6PD deficiency in this study of Thais. With the data from other Southeast Asian ethnic groups such as Laotians, G6PD Viangchan (871G>A) is probably the most common variant in non-Chinese Southeast Asian population.

Genetic interactions in the pathogenesis of neonatal hyperbilirubinemia: Gilbert's Syndrome and glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is a common condition with a worldwide distribution that has the potential for causing severe hyperbilirubinemia with bilirubin encephalopathy. Hemolysis resulting from identifiable triggers may be the cause of the jaundice in some cases, but in many, jaundice continues to occur despite avoidance of contact with known hemolytic triggers. In some G-6-PD-deficient population groups, carboxyhemoglobin studies have indicated exaggerated hemolysis; but in others, increased hemolysis has not correlated with serum total bilirubin values. As hyperbilirubinemia results from an imbalance between bilirubin production and bilirubin elimination, diminished bilirubin conjugation was suspected to contribute to the pathogenesis of hyperbilirubinemia. Serum-conjugated bilirubin fractions, reflecting intrahepatocytic bilirubin conjugation, were low in G-6-PD-deficient neonates who developed hyperbilirubinemia. This conjugated bilirubin profile was similar to that seen in adults with Gilbert's Syndrome, a condition associated with promoter polymorphism for the gene encoding the bilirubin-conjugating enzyme, UGT glucuronosyltransferase 1A1 (UGT). Whereas G-6-PD deficiency or Gilbert's Syndrome, alone, did not predispose to hyperbilirubinemia, G-6-PD-deficient neonates who also were heterozygotes or homozygotes for the variant UGT gene promoter did have significantly increased incidences of hyperbilirubinemia. Additional conditions which predispose to neonatal jaundice in the presence of Gilbert's Syndrome, include Coombs' negative ABO blood group heterospecificity, hereditary spherocytosis, and prolonged breastfeeding.Gilbert's Syndrome and G-6-PD deficiency are both common, inherited conditions. Individually, and in the absence of additional genetic or environmental factors, both are benign, and should result in minimal health disturbance or interference with the quality of life of affected individuals. However, in combination, or following exposure to environmental or other genetic factors, these benign conditions may have severe manifestations, with potentially dangerous and possibly life-threatening consequences. This review highlights the major clinical features of both Gilbert's Syndrome and G-6-PD deficiency, and surveys a series of studies related to neonatal jaundice in G-6-PD-deficient neonates culminating in the documentation of an interaction between the two conditions that is crucial to the pathogenesis of hyperbilirubinemia.