Evaluation of tumor-infiltrating lymphocytes and association with prognosis in BRCA-mutated breast cancer.

BACKGROUND: Patients with a BRCA1 or BRCA2 mutation (BRCA-mutated breast cancer) are frequently diagnosed with low differentiated and highly proliferating breast cancer characterized by high amounts of tumor-infiltrating lymphocytes (Tils). Stromal Tils (sTils) are highly prognostic in sporadic triple-negative and HER2 positive breast cancer however, their prognostic importance in BRCA-mutated breast cancers is unknown. MATERIAL AND METHODS: Formalin-fixed paraffin-embedded primary tumor tissue from 411 patients with a germline BRCA1 or BRCA2 mutation and diagnosed with early breast cancer was included. The percentage of sTils was quantified on full HE sections according to guidelines proposed by the Immuno-Oncology Biomarker in Breast Cancer Working Group. Distribution of sTils and associates with patient and tumor characteristics were assessed according to categorical sTils groups defined as low (<10%), intermediate (10-59%) and high (≥60%). Prognostic associations of sTils were evaluated as a continuous variable in univariate and multivariate models. Only follow-up time beyond date of BRCA mutation test was included. RESULTS: A large proportion had high sTils (27% in the full cohort, 36% in BRCA1-mutated, and 44% in ER negative breast cancers). Higher sTils were associated with BRCA1, ER negative breast cancer, high histological grade and medullary histology. In combined analysis for BRCA1 and BRCA2-mutated breast cancers, increasing sTils in 10% intervals were significantly associated with OS (HR 0.92, 95% CI 0.84-1.00, p = .05). For each 10% increment of sTils in BRCA1 breast cancers, a 10% reduction of mortality (adjusted HR 0.90 95% CI 0.81-0.99, p = .03) and a 13% reduction in risk of DFS-event (HR 0.87 95% CI 0.76-1.00, p = .05) was observed even after adjustment for ER status. No significant association with survival was of observed in the BRCA2 subgroup. Test for interaction of sTils and BRCA status was not statistically significant (p = .3). CONCLUSIONS: Breast cancer patients with a germline BRCA mutation had higher sTils than previously reported in sporadic breast cancers, and sTils were associated with favorable survival among BRCA carriers.

Clinical and molecular characterization of BRCA-associated breast cancer: results from the DBCG.

BACKGROUND: In breast cancer (BC) patients a cancer predisposing BRCA1/2 mutation is associated with adverse tumor characteristics, risk assessment and treatment allocation. We aimed to estimate overall- (OS) and disease-free survival (DFS) according to tumor characteristics and treatment among women who within two years of definitive surgery for primary BC were shown to carry a mutation in BRCA1/2 . MATERIAL AND METHODS: From the clinical database of the Danish Breast Cancer Group we included 141 BRCA1 and 96 BRCA2 BC patients. Estrogen receptor and HER2 status were centrally reviewed on paraffin-embedded tumor tissue. Information on risk reducing surgery was obtained from the Danish Pathology and Patient Registries and included as time-dependent variables in Cox proportional hazard models. RESULTS: Ten-year OS and DFS for BRCA1 BC patients were 78% (95% CI 69-85) and 74% (95% CI 64-81). Ten-year OS and DFS for BRCA2 BC were 88% (95% CI 78-94) and 84% (95% CI 74-91). BRCA1 BC patients as compared to BRCA2 BC patients had a higher risk of BC relapse or non-breast cancer within ten years of follow-up, independent of ER status (adjusted HR 2.78 95% CI 1.28-6.05, p = .01), but BRCA mutation was not associated with OS (adjusted HR 1.98, 95% CI 0.87-4.52, p = .10). In multivariate analysis, including both BRCA1 and BRCA2 carriers, no chemotherapy was associated with a higher risk of death (adjusted OS HR 3.58, 95% CI 1.29-9.97, p = .01) and risk reducing contralateral mastectomy (RRCM) was associated with a significantly reduced risk of death (adjusted OS HR 0.42, 95% CI =0.21-0.84, p = .01). CONCLUSION: Difference in OS between BRCA1 and BRCA2 BC patients could be ascribed to tumor-biology. BRCA1 BC patients may have a shorter ten-year DFS than BRCA2 BC patients. Chemotherapy and risk reducing contralateral mastectomy reduce mortality for both BRCA1 and BRCA2 BC patients.

Multivariate modelling of endophenotypes associated with the metabolic syndrome in Chinese twins.

AIMS/HYPOTHESIS: The common genetic and environmental effects on endophenotypes related to the metabolic syndrome have been investigated using bivariate and multivariate twin models. This paper extends the pairwise analysis approach by introducing independent and common pathway models to Chinese twin data. The aim was to explore the common genetic architecture in the development of these phenotypes in the Chinese population. METHODS: Three multivariate models including the full saturated Cholesky decomposition model, the common factor independent pathway model and the common factor common pathway model were fitted to 695 pairs of Chinese twins representing six phenotypes including BMI, total cholesterol, total triacylglycerol, fasting glucose, HDL and LDL. Performances of the nested models were compared with that of the full Cholesky model. RESULTS: Cross-phenotype correlation coefficients gave clear indication of common genetic or environmental backgrounds in the phenotypes. Decomposition of phenotypic correlation by the Cholesky model revealed that the observed phenotypic correlation among lipid phenotypes had genetic and unique environmental backgrounds. Both pathway models suggest a common genetic architecture for lipid phenotypes, which is distinct from that of the non-lipid phenotypes. The declining performance with model restriction indicates biological heterogeneity in development among some of these phenotypes. CONCLUSIONS/INTERPRETATION: Our multivariate analyses revealed common genetic and environmental backgrounds for the studied lipid phenotypes in Chinese twins. Model performance showed that physiologically distinct endophenotypes may follow different genetic regulations.

Candidate region linkage analysis in twins discordant or concordant for depression symptomatology.

Genetic risk factors contribute considerably to both clinical affective disorders and subsyndromal mood level. There is moreover evidence to suggest that the genetic basis of bipolar disorder and unipolar depression overlap to some extent, and several linkage analyses have suggested evidence for a common susceptibility locus in affective disorders on chromosome 12q24. In this study we investigated the chromosome 12 candidate region for linkage to the mean level of depression symptomatology, over a 10-year follow-up, using a highly informative sample of concordant and discordant twin pairs selected from 4,731 participants of the Longitudinal Study of Ageing Danish Twins. Our results showed suggestive evidence of linkage to this region with a peak LOD score of 1.91 for marker D12S1634 located at 148 cM, and thus indicates that the previously identified disease locus at 12q24 is also a general vulnerability locus affecting the normal range of mood.

Association analysis identifies TLR7 and TLR8 as novel risk genes in asthma and related disorders.

BACKGROUND: Toll-like receptors (TLRs) are structurally and functionally related and play important roles in the innate and adaptive immune system. By genome scanning, evidence of linkage between chromosome Xp22 and asthma and related atopic disorders has previously been obtained. Xp22 harbours the TLR7 and TLR8 genes. METHODS: The involvement of TLR7 and TLR8 in the aetiology of asthma and related disorders was investigated by a family based association analysis of two independently ascertained family samples comprising 540 and 424 individuals from 135 and 100 families, respectively. Ten affected individuals from families showing evidence of linkage to Xp22 were screened for sequence variations in TLR7 and 8, and nine single nucleotide polymorphisms (SNPs) identified were tested for association. RESULTS: In both samples, significant associations were observed for single SNPs and haplotypes of both TLR7 and 8 in all four phenotypes investigated: asthma, rhinitis, atopic dermatitis and increased specific IgE. The most significant association was seen for rs2407992 (TLR8) in asthma (p = 0.00023, sample A and B combined, recessive model). In TLR7, rs179008 showed the strongest association. Both rs179008 and rs2407992 are of putative functional significance, potentially affecting TLR7 processing and TLR8 splicing, respectively. Haplotypes comprising the major alleles of these two SNPs were overtransmitted to the affected offspring (eg, p = 0.00012 in asthma, combined sample, additive model). CONCLUSION: The results provide strong evidence that TLR7 and 8 may confer susceptibility to asthma and related atopic disorders and highlight these receptors as interesting targets for individualised, causally directed treatment.

Evidence for an asthma risk locus on chromosome Xp: a replication linkage study.

BACKGROUND: Asthma is a complex genetic disorder characterized by chronic inflammation in the airways. Identification of genetic risk factors for asthma has been complicated due to genetic heterogeneity and influence from environmental risk factors. Despite the fact that multiple genetic linkage studies have been carried out the results are still conflicting and call for replication experiments. A Danish genome-wide scan has prior reported evidence for candidate regions for asthma susceptibility genes on chromosomes 1p, 5q, 6p, 12q and Xp. Linkage to chromosome 12q was later confirmed in the same replication sample as used in the present study. The aim of the study was to replicate linkage to candidate regions for asthma in an independent Danish sample. METHODS: We performed a replication study investigating linkage to candidate regions for asthma on chromosomes 1p36.31-p36.21, 5q15-q23.2, 6p24.3-p22.3, and Xp22.31-p11.4 using additional markers in an independent set of 136 Danish asthmatic sib pair families. RESULTS: Nonparametric multipoint linkage analyses yielded suggestive evidence for linkage to asthma to chromosome Xp21.2 (MLS 2.92) but failed to replicate linkage to chromosomes 1p36.31-p36.21, 5q15-q23.2 and 6p24.3-p22.3. CONCLUSIONS: The replication results provide evidence for chromosome Xp21 to harbour a susceptibility gene for asthma in the Danish population. To our knowledge, the study is the first to replicate evidence for linkage to chromosome X. A susceptibility gene for asthma on chromosome X could potentially explain observed gender differences in asthma prevalence.

Alpha-cardiac actin is a novel disease gene in familial hypertrophic cardiomyopathy.

We identified the alpha-cardiac actin gene (ACTC) as a novel disease gene in a pedigree suffering from familial hypertrophic cardiomyopathy (FHC). Linkage analyses excluded all the previously reported FHC loci as possible disease loci in the family studied, with lod scores varying between -2.5 and -6.0. Further linkage analyses of plausible candidate genes highly expressed in the adult human heart identified ACTC as the most likely disease gene, showing a maximal lod score of 3.6. Mutation analysis of ACTC revealed an Ala295Ser mutation in exon 5 close to 2 missense mutations recently described to cause the inherited form of idiopathic dilated cardiomyopathy (IDC). ACTC is the first sarcomeric gene described in which mutations are responsible for 2 different cardiomyopathies. We hypothesize that ACTC mutations affecting sarcomere contraction lead to FHC and that mutations affecting force transmission from the sarcomere to the surrounding syncytium lead to IDC.

Highly significant linkage to chromosome 3q13.31 for rhinitis and related allergic diseases.

BACKGROUND: Allergic diseases such as asthma and rhinitis have closely related phenotypes and often occur with atopy. They show strong familial and intra-individual clustering, suggesting overlapping disease aetiology. Various loci and candidate genes have been suggested to underlie allergy. Many or all are still inconclusive. Following genome-wide scans on multiple phenotypes, we previously suggested that chromosome 3q13.12-q21.2 harbours an allergy locus. OBJECTIVE: To identify candidate loci in the Danish population, two additional independent sets of sib-pair families were fine-scale mapped in candidate regions showing maximum likelihood scores (MLS) > or =1.5 in the genome-wide scans. RESULTS: Twenty eight microsatellite markers in a denser map on chromosome 3q were analysed in 236 allergy sib-pair families including 125 sib pairs with rhinitis. We report significant evidence for linkage to chromosome 3q13.31 for rhinitis (MLS 5.55, identity by descent (IBD) 63.9%) and atopy (increased specific immunoglobulin E) (MLS 3.71, IBD 61.7%). We obtained an MLS of 5.1 (IBD 67.3%) at 3q13.31 when sib pairs with both rhinitis and atopy were analysed. CONCLUSION: This study reports the first statistically significant evidence for a genetic susceptibility locus for rhinitis and to our knowledge shows the most significant evidence to date of linkage for any allergy phenotype.

Nordic collaborative study of the BARD1 Cys557Ser allele in 3956 patients with cancer: enrichment in familial BRCA1/BRCA2 mutation-negative breast cancer but not in other malignancies.

BACKGROUND: BARD1 was originally identified as a BRCA1-interacting protein but has also been described in tumour-suppressive functions independent of BRCA1. Several studies have indicated that the BARD1 gene is a potential target for germline changes predisposing to breast and ovarian cancer. The C-terminal Cys557Ser change has previously been uncovered to associate with an increased risk of breast cancer and was recently shown to result in defective apoptotic activities. AIM AND METHODS: Conformation-sensitive gel electrophoresis, minisequencing, TaqMan assays, denaturing high-performance liquid chromatography analysis and DNA sequencing were used to investigate the prevalence of the Cys557Ser allele in a large Nordic case-control study cohort consisting of 2906 patients with breast or ovarian cancer, 734 with prostate cancer, 188 with colorectal cancer, 128 men with breast cancer, and 3591 controls from Finland, Iceland, Denmark, Sweden and Norway. RESULTS: The frequency of the BARD1 Cys557Ser variant seemed to increase among patients from families with breast or ovarian cancer lacking BRCA1 or BRCA2 mutations: a significant difference was obtained compared with controls (6.8% v 2.7%; p<0.001; odds ratio (OR) 2.6; 95% confidence interval (CI) 1.7 to 4.0) and with patients from BRCA1/BRCA2 mutation-positive families (6.8% v 2.2%; p = 0.01; OR 3.2; 95% CI 1.2 to 8.3). In contrast, no major association with male breast, ovarian, colorectal or prostate cancer was observed. Additionally, a novel BARD1 allele resulting in Ser558Pro was identified in familial breast cancer cases. CONCLUSION: These results provide further evidence that BARD1 Cys557Ser confers a slightly increased risk of breast cancer in women.

A longitudinal study of the effect of GSTT1 and GSTM1 gene copy number on survival.

Deletions of the glutathione S-transferase superfamily genes GSTT1 and GSTM1 has been associated with oxidative stress related diseases and recently explored as factors implicated in longevity as well. Reported results have been conflicting, which may partially be caused by the traditional use of assays unable to discriminate between carriers of one or two functional genes. Using a quantitative realtime PCR method facilitating quantification of gene copy number, we evaluated the influence of GSTT1 and GSTM1 gene deletions on longevity in a longitudinal study of 681 elderly Danish twins. The mean follow-up time was 7.6 years and during this time a total of 294 deaths occurred. The results demonstrated a non-significant trend for carriage of two copies of the GSTM1 functional gene to be a protective factor, whereas both heterozygosity and homozygosity for the GSTT1 functional gene was associated with a moderate but significant increased mortality in women (hazard rate 2.46 (CI95: 1.43-4.23) and 2.22 (CI95: 1.25-3.94) for one and two alleles, respectively). To our knowledge, this is the first longitudinal study exploring the influence of GST gene polymorphisms on longevity and these data implies that GST gene copy numbers do affect mortality risk in the elderly.

Allelic loss of 16q23.2-24.2 is an independent marker of good prognosis in primary breast cancer.

Allelic loss, detected as a loss of heterozygosity (LOH) on the long arm of chromosome 16, is an early and frequent event in breast cancer. Despite this, the clinical significance of LOH on 16q has been very poorly studied. In this study, corresponding blood and tumor samples from 199 clinically well-characterized primary breast cancer patients were analyzed for LOH with the highly polymorphic microsatellite marker D16S511, located at 16q23.2-24.2. 61% of 168 informative tumors showed LOH. Univariate and multivariate analysis found a highly significant association between LOH at 16q23.2-24.2 and freedom from distant metastases, disease-free survival, and overall survival, respectively. No association was found with other clinical parameters such as menopausal status, tumor size, lymph node status, histopathology, and lymph node capsule invasion. This makes allelic loss of 16q23.2-24.2 an independent marker of good prognosis for primary breast cancer.

Identification, molecular cloning, expression and chromosome mapping of a family of transformation upregulated hnRNP-K proteins derived by alternative splicing.

Acidic nuclear proteins (M(r) between 64,000 and 66,000; pI 4.9 to 5.5) that are highly upregulated in transformed cells and that belong to the hnRNP-K family have been identified using a monoclonal antibody (mAB B4B6) that distinguish between quiescent and proliferating human keratinocytes. The family, which is composed of four major proteins (hnRNPs-K A, B, C and D) and their modified forms, is present in similar overall levels in quiescent and proliferating normal keratinocytes although clear differences were observed in the levels of some of the individual variants. Immunofluorescence staining of proliferating normal keratinocytes with mAB B4B6 showed that about 40% of the keratinocytes, corresponding mainly to G1 and to half of the cells in S-phase, reacted with the antibody depicting a dotted, nucleoplasmic staining that excluded the nucleolus. Only 3 to 4% of the quiescent keratinocytes reacted with the antibody while simian virus 40 (SV40) transformed keratinocytes (K14) stained constitutively throughout the cell cycle. Using mAB B4B6 as a probe we cloned a cDNA coding for one member of the family (hnRNP-K B) and this was used to screen for additional family members. Sequencing of the positive clones revealed four different cDNAs, all resulting from alternative splicing of a common primary transcript of a gene that mapped to chromosome 9. Expression of the cDNAs in the vaccinia virus system confirmed their identity as hnRNPs-K A, B, C and D and showed that their modified forms are phosphorylated. All four hnRNPs bound poly(rC) on NorthWestern blots, although the more acidic of the phosphorylated forms, did so at a much reduced level. hnRNP-K has been implicated in pre-mRNA metabolism of transcripts containing cytidine-rich sequences and our results point towards a role during cell cycle progression.

Acute hypoxia induces upregulation of microRNA-210 expression in glioblastoma spheroids.

AIM: Tumor hypoxia and presence of tumor stem cells are related to therapeutic resistance and tumorigenicity in glioblastomas. The aim of the present study was therefore to identify microRNAs deregulated in acute hypoxia and to identify possible associated changes in stem cell markers. MATERIALS & METHODS: Glioblastoma spheroid cultures were grown in either 2 or 21% oxygen. Subsequently, miRNA profiling was performed and expression of ten stem cell markers was examined. RESULTS: MiRNA-210 was significantly upregulated in hypoxia in patient-derived spheroids. The stem cell markers displayed a complex regulatory pattern. CONCLUSION: MiRNA-210 appears to be upregulated in hypoxia in immature glioblastoma cells. This miRNA may represent a therapeutic target although it is not clear from the results whether this miRNA may be related to specific cancer stem cell functions.

Identification of novel and known mutations in the genes for keratin 5 and 14 in Danish patients with epidermolysis bullosa simplex: correlation between genotype and phenotype.

Epidermolysis bullosa simplex (EBS) is a group of autosomal dominant inherited skin diseases caused by mutations in either the keratin 5 (K5) or the keratin 14 (K14) genes and characterized by development of intraepidermal skin blisters. The three major subtypes of EBS are Weber-Cockayne, Koebner, and Dowling-Meara, of which the Dowling-Meara form is the most severe. We have investigated five large Danish families with EBS and two sporadic patients with the Dowling-Meara form of EBS. In the sporadic Dowling-Meara EBS patients, a novel K14 mutation (N123S) and a previously published K5 mutation (N176S) were identified, respectively. A novel K14 mutation (K116N) was found in three seemingly unrelated families, whereas another family harbored a different novel K14 mutation (L143P). The last family harbored a novel K5 mutation (L325P). The identified mutations were not present in more than 100 normal chromosomes. Six polymorphisms were identified in the K14 gene and their frequencies were determined in normal controls. These polymorphisms were used to show that the K14 K116N mutation was located in chromosomes with the same haplotype in all three families, suggesting a common ancestor. We observed a strict genotype-phenotype correlation in the investigated patients as the same mutation always resulted in a similar phenotype in all individuals with the mutation, but our results also show that it is not possible to predict the EBS phenotype merely by the location (i.e., head, rod, or linker domains) of a mutation. The nature of the amino acid substitution must also be taken into account.

Familial isolated hyperparathyroidism as a variant of multiple endocrine neoplasia type 1 in a large Danish pedigree.

We report here our genetic findings of a family in which 14 members were affected with isolated primary hyperparathyroidism. Hyperparathyroidism is the main feature of multiple endocrine neoplasia type 1 (MEN1), making the recently cloned MEN1 gene a prime candidate gene in this family. Significantly positive lod scores were achieved with D11S4946 (3.36) and D11S4940 (3.53), and by combining the results from these two markers, a maximum positive lod score of 4.12 at recombination fraction 0.00 was obtained. Mutation analysis of MEN1 performed by full sequencing identified a missense mutation in exon 4, causing an amino acid change from glutamine to proline at codon 260. This mutation (Q260P) was present in all affected family members, and the inheritance of the mutation was in complete agreement with the disease-associated haplotype. In comparison with the recent functional studies of the menin protein interactions, this mutation is located in a region with little or no binding activity to JunD and activating protein-1 transcription factor. We conclude that some of the familial isolated primary hyperparathyroidism families constitute a milder variant of MEN 1, which is associated with a functionally milder missense mutation.

Allergic rhinitis--a total genome-scan for susceptibility genes suggests a locus on chromosome 4q24-q27.

Allergic rhinitis is a common disease of complex inheritance and is characterised by mucosal inflammation caused by allergen exposure. The genetics of closely related phenotypes such as asthma, atopy and to some extend atopic dermatitis has attracted attention in recent years. Genetic reports of allergic rhinitis on the contrary have as yet been most sparse. To identify candidate regions holding genes for allergic rhinitis we performed a total genome-scan on affected sib-pair families. From 100 Danish sib-pair families selected for allergy, families containing sib-pairs matching a phenotype definition of both clinical allergic rhinitis and confirmed specific allergy were chosen. Thirty-three affected sib-pair families qualified for the scan that was undertaken using 446 microsatellite markers. Non-parametric linkage results were obtained from MAPMAKER/SIBS computer program. The study revealed one major candidate region on chromosome 4q24-q27 (LOD=2.83) and eight minor candidate regions 2q12-q33, 3q13, 4p15-q12, 5q13-q15, 6p24-p23, 12p13, 22q13, and Xp21 (LOD=1.04-1.63) likely to contain susceptibility genes for allergic rhinitis. Our findings did not support a previous report of linkage of allergic rhinitis to chromosome 12q14-q24 but they added positive evidence to the asthma and atopy candidate regions 2q33 and 6p23. Further identification of the specific genes involved in allergic rhinitis will give opportunities for improved diagnosis and treatment.

Cathepsin K gene mutations and 1q21 haplotypes in at patients with pycnodysostosis in an outbred population.

The molecular genetics of the autosomal recessive disorder pycnodysostosis was studied in five independent families from an outbred Caucasian population. We found two new mutations and one recently described mutation in the cathepsin K gene by sequencing DNA from eight patients with pycnodysostosis: a one base transition in exon8, c926T > C, causing a single amino acid substitution leucine-->proline, L309P; A 3' splice site mutation in intron 2, c121-1G > A, causing deletion of all exon 3, 41V-81Mdel; and the exon 3 missense mutation c236G > A leading to residue G79E. In three of the families patients were homozygous for 926T > C. In the remaining two families patients were heterozygous for 926T > C and 121-1G > A in one case, and for 926T > C and 236G > A in the other case. Assays using genomic DNA were developed for all three mutations. We tested 150 healthy control persons and observed the mutation frequencies: 0 to 300 for 121-1G > A and 236G > A and 1 to 150 for 926T > C. One patient from each family was haplotyped with eight microsatellite markers surrounding the cathepsin K gene on chromosome 1q21. A very rare, P = 1.8 x 10(-6) to P = 0.0004, and highly preserved area around the presumed disease locus was common to all the patients. This haplotype was found on seven chromosomes identical by state, IBS, out of the possible eight carrying the 926T > C mutation. Founder effect, locus homogeneity, and allele heterogeneity regarding pycnodysostosis within this population are discussed. Finally, the first pregnancy and delivery described in a patient with pycnodysostosis is reported.

A new locus for Seckel syndrome on chromosome 18p11.31-q11.2.

Seckel syndrome (MIM 210600) is a rare autosomal recessive disorder with a heterogeneous appearance. Key features are growth retardation, microcephaly with mental retardation, and a characteristic 'bird-headed' facial appearance. We have performed a genome-wide linkage scan in a consanguineous family of Iraqi descent. By homozygosity mapping a new locus for the syndrome was assigned to a approximately 30 cM interval between markers D18S78 and D18S866 with a maximum multipoint lod score of 3.1, corresponding to a trans-centromeric region on chromosome 18p11.31-q11.2. This second locus for Seckel syndrome demonstrates genetic heterogeneity and brings us a step further towards molecular genetic delineation of this heterogeneous condition.

Human ClpP protease: cDNA sequence, tissue-specific expression and chromosomal assignment of the gene.

We identified three overlapping human expressed sequence tags with significant homology to the E. coli ClpP amino sequence by screening the EMBL nucleotide database. With this sequence information we applied 5' and 3'-rapid amplification of cDNA ends (RACE) to amplify and sequence human clpP cDNA in two overlapping fragments. The open reading frame encodes a 277 amino acid long precursor polypeptide. Two ClpP specific motifs surrounding the active site residues are present and extensive homology to ClpP's from other organisms was observed. Northern blotting showed high relative expression levels of clpP mRNA in skeletal muscle, intermediate levels in heart, liver and pancreas, and low levels in brain, placenta, lung and kidney. By analysis of human/rodent cell hybrids the human clpP gene was assigned to chromosome 19.

The human lactase-phlorizin hydrolase gene is located on chromosome 2.

The lactase-phlorizin hydrolase gene was assigned to chromosome 2 by analysis of Southern blots of DNA from a panel of human-rodent cell hybrids containing characteristic sets of human chromosomes The hybridization probe used was a recently isolated cDNA clone of the human lactase-phlorizin hydrolase gene.