Classification of germline variants identified in cancer predisposition genetic testing - consensus of the CZECANCA consortium

BACKGROUND

Hereditary cancer syndromes are an important subset of malignant cancers caused by pathogenic variants in one of many known cancer predisposition genes. Diagnosis of cancer predisposition is based on genetic testing using next-generation sequencing. This allows many genes to be analysed at once, increasing the number of variants identified. The correct classification of the variants found is essential for the clinical interpretation of genetic test results.

PURPOSE

The aim of this study is to summarise the rules for classifying identified variants within individual laboratories and to present the process for creating a common classification. In the Czech Republic, the sharing of identified genetic variants and the development of their consensus classification among national laboratory diagnostic communities is carried out within the Czech Cancer Panel for Clinical Application (CZECANCA) consortium of scientific and diagnostic oncogenetic laboratories. Consensus for variant classification follows a defined protocol. Sharing the results and consensus classification accelerates and refines the release of genetic test results, harmonises results between laboratories and thus contributes to improving the care of individuals at high risk of cancer and their relatives.

Polygenic risk score (PRS) and its potential for breast cancer risk stratification

BACKGROUND

Breast cancer is a complex, multifactorial disease influenced by many genetic factors. Besides the relatively rare pathogenic variants in high or moderate penetrant cancer predisposition genes, breast cancer risk is modified by numerous low risk alleles considered to be polygenic genetic factors. While the risks associated with individual polygenic loci are negligible, its cumulative effect can reach clinically significant values and it can be expressed as a polygenic risk score (PRS). PRS is recently considered to be a possible tool improving assessment of absolute and cumulative risks at the individual level.

PURPOSE

Several single nucleotide polymorphism sets for PRS assessment have recently been developed and prepared for their implementation into clinical practice. The following text aims to explain the fundamental principles of the PRS assessment and its interpretation as a candidate prediction tool. The use of the PRS should always depend on genetic analysis of pathogenic variants in cancer predisposition genes including its current limitations.

[PALB2 as Another Candidate Gene for Genetic Testing in Patients with Hereditary Breast Cancer in Czech Republic]

BACKGROUND

The PALB2 (FANCN) gene was identified as a component of endogenous BRCA2 complex that encodes a DNA repair protein participating along with BRCA1 and BRCA 2 proteins in DNA double-strand break repair. Hereditary PALB2 mutations are associated with an increased risk of breast and pancreatic cancers in heterozygotes. Breast cancer risk for PALB2 mutation carriers has recently been estimated at 33-58% depending on family history of breast cancer; pancreatic cancer risk in carriers of PALB2 mutations has not been precisely quantified, yet.

MATERIALS AND RESULTS

Results of a study identifying PALB2 mutations in high-risk, BRCA1/2-negative, breast and/or ovarian cancer patients in the Czech Republic indicate that the frequency of hereditary PALB2 mutations in our population is quite high. Interestingly, almost 20% of all recognized mutations comprised large genomic rearrangements. The highest proportion of PALB2 mutations (comparable with the number of mutations reported for BRCA2) was found in a subgroup of hereditary breast cancer patients (5.5%). Frequency of mutations in an independent group of Czech unselected pancreatic cancer patients was approximately 1.3%.

CONCLUSION

Considering the frequency of pathogenic, hereditary PALB2 mutations in our population, their phenotypic similarity to BRCA2, and expected risk of breast cancer associated with PALB2 mutations, its screen-ing (including large genomic rearrangements) should be encouraged in patients from hereditary breast cancer families. The follow-up of pathogenic PALB2 mutation carriers should be similar to that in BRCA2 mutation carriers, enabling early diagnosis, prevention, and possible targeted therapy. Preventive surgical interventions for the carriers could be considered in case of strong family cancer history and evident segregation of a pathogenic mutation with a tumor phenotype. Additional analysis of various cancer patient populations and further meta-analyses will be necessary for accurate assessment of PALB2 gene penetrance and its significance for the risk of pancreatic and other cancers.

[CZECANCA: CZEch CAncer paNel for Clinical Application-- Design and Optimization of the Targeted Sequencing Panel for the Identification of Cancer Susceptibility in High-risk Individuals from the Czech Republic]

Individuals with hereditary cancer syndromes form a minor but clinically important subgroup of oncology patients, comprising several thousand cases in the Czech Republic annually. In these patients, the identification of pathogenic mutations in cancer susceptibility genes has an important predictive and, in some cases, prognostic value. It also enables rational preventive strategies in asymptomatic carriers from affected families. More than 150 cancer susceptibility genes have been described so far; however, mutations in most of them are very rare, occurring with substantial population variability, and hence their clinical interpretation is very complicated. Diagnostics of mutations in cancer susceptibility genes have benefited from the broad availability of next-generation sequencing analyses using targeted gene panels. In order to rationalize the diagnostics of hereditary cancer syndromes in the Czech Republic, we have prepared the sequence capture panel "CZECANCA", targeting 219 cancer susceptibility genes. Besides more than 50 clinically important high- and moderate-penetrance susceptibility genes, the panel also targets less common candidate genes with uncertain clinical relevance. Alongside the panel design, we have optimized the analytical and bioinformatics pipeline, which will facilitate establishing a collective nationwide database of genotypes and clinical data from the analyzed individuals. The key objective of this project is to provide diagnostic laboratories in the Czech Republic with a reliable procedure and collective database improving the clinical utility of next-generation sequencing analyses in high-risk patients, which would help improve the interpretation of rare or population-specific variants in cancer susceptibility genes.

[The clinical importance of a genetic analysis of moderate-risk cancer susceptibility genes in breast and other cancer patients from the Czech Republic]

BACKGROUND

Analysis of the major breast cancer (BC) predisposition genes BRCA1 and BRCA2 enables identification of high-risk individuals. Specialized programs enrolling the carriers of BRCA1/2 mutations facilitate an improvement in prevention and early diagnostics in asymptomatic individuals and rationalize the selection of individualized treatment in case of a BC onset. However, the carriers of mutations in the major predisposition genes represent only approximately 25% of cases among high-risk BC patients. Numerous candidate predisposing genes for breast and other cancers have recently been identified. The risk of cancer development associated with alterations in these genes is lower, and there is a considerable population variability in different regions worldwide.

AIM

We have performed mutation analyses of moderate-risk cancer susceptibility genes to evaluate their clinical importance for genetic counseling in high-risk patients suffering from breast and other cancers in the Czech population.

RESULTS

Czech oncological patients were analysed for mutation in ATM, CHEK2, NBS1 (NBN) and PALB2 genes. The majority of analyzed individuals represent the population of high-risk BRCA1/2-negative BC patients.

CONCLUSIONS

Based on results of this study, we recommend an analysis of recurrent truncating mutations in the CHEK2 gene (the c.1100delC mutation and a large deletion affecting exons 9-10) in BRCA1/2-negative patients from high-risk BC families. A clinical assessment of missense variants in CHEK2 is not suitable. A routine mutation analysis of the ATM and NBS1 (NBN) genes is not recommended in BC patients due to the low frequency of alterations in these genes in the Czech Republic. An identification of truncating mutations in the PALB2 gene is important in BRCA1/2-negative BC patients from families with a strong history of BC (HBC families). The frequency of PALB2 mutations may be comparable to the frequency of mutations in the BRCA2 gene in Czech HBC families.

Oxidative stress and inflammation in pregnancy

Pregnancy is a period when increased oxidative stress can be expected. We have focused especially on oxidative stress and inflammation in the period of pregnancy, when prenatal screening is usually performed. We determined advanced oxidation protein products (AOPPs), C-reactive protein (CRP) and anticardiolipin antibodies (ACA) IgG and IgM levels in the serum of 86 pregnant women in the 1st trimester and 102 pregnant women in the 2nd trimester. AOPP levels in the maternal serum of pregnant women were significantly higher in the 1st and 2nd trimesters than they were in that of non-pregnant women (p<0.0001, p<0.001, respectively). Maternal serum CRP levels, too, were increased compared with those in non-pregnant women (1st and 2nd trimester versus non-pregnant women p<0.05, p<0.005, respectively). Just as with AOPPs and CRP, the ACA IgG levels in pregnant women were significantly higher in both trimesters than they were in non-pregnant women (1st and 2nd trimesters versus non-pregnant women p<0.05, p<0.001, respectively). Maternal serum CRP levels correlated positively with AOPPs in the 2nd trimester (r = 0.504, p<0.05). The increased levels of AOPPs, CRP and ACA IgG in the 1st and 2nd trimesters may reflect a maternal response to inflammatory and oxidative stress in pregnant women.

Synergy of serum and cerebrospinal fluid antibodies against axonal cytoskeletal proteins in patients with different neurological diseases

Autoantibodies against different axonal cytoskeletal proteins [the light (NFL) and medium (NFM) subunit of neurofilament and tubulin (TUB)] in serum and cerebrospinal fluid may be generated in response to the release of cytoskeleton from damaged neurons. We studied the relationships among these autoantibodies. Paired cerebrospinal fluid (CSF) and serum samples were obtained from 47 multiple sclerosis (MS) patients, 14 patients with neurodegenerative diseases, 21 patients with various neurological diseases and 16 normal control subjects. Levels of antibodies against NFL, NFM and TUB were related to each other in CSF in all groups, whereas close association of anti-cytoskeletal antibodies in serum was found in the MS group only. A concordant spectrum of anti-cytoskeletal antibodies is present in serum of MS patients, unlike in other neurological patients. The synergy between the spectrum of anti-cytoskeletal antibodies in serum and CSF might be one of the immunological features typical for the MS patients.

Antibodies against light neurofilaments in multiple sclerosis patients

OBJECTIVES

Axonal damage in multiple sclerosis (MS) may be reflected by antibodies against axon-specific proteins - the light subunit of neurofilaments (NFL).

MATERIALS AND METHODS

The serum and cerebrospinal fluid obtained from 58 MS patients, 24 normal controls (CN), 49 control patients with miscellaneous diseases (CD) and 31 patients with neurodegenerative disorders (CDEG) were tested for both immunoglobulin G and M antibodies against NFL, using an ELISA.

RESULTS

Intrathecal IgG antibodies to NFL were elevated in MS patients compared with that in CD patients (P = 0.001) and were not related to clinical variables. No differences in IgM anti-NFL levels were found between the MS and CN/CD groups. IgM to NFL was higher in the CDEG group than in either the CD group or even the MS group (P < 0.0005). CONCLUSIONS - Intrathecal IgM or IgG antibodies to NFL are not useful surrogate markers for axonal damage or disease subtypes in MS.

Carbonyl and oxidative stress in patients with breast cancer--is there a relation to the stage of the disease?

Oxidative and carbonyl stress may, on one hand, contribute to the progression of cancer, on the other hand, they may have some antiproliferative effects. We examined serum levels of AGEs (advanced glycation end-products), CML (carboxymethyllysine) and AOPP (advanced oxidation protein products) in 86 patients with breast cancer subdivided based on the clinical stage (TNM classification), histologic grading, expression of hormonal and C-erb B2 receptors and in 14 healthy age-matched women as controls. Breast cancer patients had higher serum concentrations of AGEs (325,581 +/- 66,037 vs. 271,322 +/- 34,826 AU, p < 0.01) even in the early stage of the disease; patients with advanced breast cancer (stage III and IV) had significantly higher both AGEs and AOPP (113.0 +/- 44.9 vs. 78.1 +/- 28.4 micromol/l, p < 0.05) levels, not only compared to controls, but also compared to stages I and II. Serum levels of AOPP were higher in patients having only weakly positive expression of C-erb 2/Her-neu compared to controls and the patients having the highest C-erb2/Her-neu expression. Serum concentrations of AGEs in patients with breast cancer correlated with the age and also with the serum concentration of AOPP.

IN CONCLUSION

breast cancer patients had an early increase of AGEs (marker of the carbonyl stress) followed by further increase of AGEs and elevation of AOPP (marker of oxidative stress) in patients with progressive disease. As the clinical significance of these observations is currently uncertain further studies are clearly warranted, especially with respect to their potential therapeutic implications.

Pregnancy-associated plasma protein-A in patients with cerebrovascular diseases--a pilot study

Pregnancy-associated plasma protein-A (PAPP-A) was described as a novel marker of acute coronary syndrome. The aim of our study was to investigate how serum pregnancy-associated plasma protein-A (PAPP-A) levels change in patients with ischaemic stroke and intracerebral haemorrhage and to evaluate if PAPP-A might be a marker not only of myocardial infarction but also a useful parameter in cerebrovascular disorders. 43 patients with acute cerebrovascular events were divided into 3 groups--patients with ischaemic stroke (n=16), patients with intracranial haemorrhage (n=10) and patients with both ischaemic stroke and coronary artery disease (n=17). The control group consisted of 12 subjects. PAPP-A was measured by TRACE (Time Resolved Amplified Cryptate Emission) technology. PAPP-A levels in patients with intracranial haemorrhage and those with both ischaemic stroke and coronary artery disease were increased in comparison with the control group (p<0.005, p<0.01, respectively) as well as with patients with ischaemic stroke only (p<0.01, p<0.05, respectively). A positive correlation between PAPP-A and total cholesterol in patients with both ischaemic stroke and coronary artery disease (r=0.497, p<0.05) was observed. Serum PAPP-A levels in all studied patients correlated positively with serum creatinine (r=0.395, p<0.05). PAPP-A levels are increased in patients with intracranial haemorrhage and in the patients whose ischaemic stroke is associated with coronary artery disease. The atherosclerotic process may contribute to increased serum PAPP-A levels. PAPP-A may be a marker of increased risk of atherothrombotic events in general.

[Advanced glycation and oxidation products in patients with atherosclerosis]

BACKGROUND

Oxidative stress can potentiate atherogenesis via modification of biological structures and formation of new compounds, e.g. advanced glycation end products (AGEs) and advanced oxidation protein products (AOPP). The aim of the study was to determine AGEs and AOPP in patients with atherosclerosis, effect of statin therapy and relationship to parameters of lipid metabolism.

METHODS AND RESULTS

AGEs (carboxymethyllysine - ELISA and fluorescent AGEs - spectrofluorimetry) and AOPP (spectrophotometry) were assessed in 42 patients with atherosclerosis and 21 healthy controls. AGEs are significantly elevated in patients with atherosclerosis in comparison with healthy subjects (carboxymethyllysine 9.02+/-1.66 microg/g prot. vs 7.52+/-1.18 microg/g prot., p<0.001, fluorescent AGEs 4.39 x 103+/-1.15 x 103 AU/g prot. vs 3.78 x 103+/-0.52 x 103 AU/g prot., p<0.001). Mean AOPP concentrations are also slightly higher, but this elevation is not quite significant (95.0+/-42.9 micromol/l vs 79.7+/-28.2 micromol/l, p=0.096). AGEs and AOPP correlate significantly with each other and with selected lipids. Patients with atherosclerosis treated with statins have slightly lower CML, AGEs and AOPP (it did not reach the statistical significance).

CONCLUSIONS

Advanced glycoxidation products are elevated in patients with atherosclerosis and are related to parameters of lipid metabolism. Glycoxidation might be possibly therapeutically influenced by statins; however, further clinical studies are required to confirm this hypothesis.

Increased Levels of Pregnancy-Associated Plasma Protein A Are Associated with Mortality in Hemodialysis Patients: Preliminary Results

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic indicator of acute coronary syndrome. This protein is elevated in hemodialysis (HD) patients and is closely related to inflammation and oxidative stress. The aim of our pilot study was to find out whether PAPP-A is related to mortality in HD patients. 40 HD patients in a stable clinical state (20 men and 20 women, mean age 69 +/- 12 years) were enrolled in the study and followed up for 20 months. PAPP-A was assessed immunochemically (TRACE method) in serum samples (before the HD session) at the beginning of the observation period. During the follow-up, 22 patients died, 15 of them due to cardiovascular events. PAPP-A levels were significantly higher in the patients who died, compared to living HD patients: 26.8 (21.6-36.8) vs. 20 (14.9-26.6) mU/l, p = 0.034. PAPP-A could also be a new prognostic marker in hemodialysis patients, probably due to its close association with cardiovascular risk. More extensive studies are required to confirm this hypothesis.

Relationship of pregnancy-associated plasma protein-a to renal function and dialysis modalities

BACKGROUND

The aim of the study was to determine pregnancy-associated plasma protein-A (PAPP-A), which was recently described as a new marker of cardiovascular events, in patients with chronic renal insufficiency/failure and to find out its relationship to renal function and to prominent markers of oxidative stress (advanced oxidation protein products--AOPP) and inflammation (C-reactive protein--CRP).

METHODS

The studied group consisted of 36 chronic hemodialysis patients (HD), 10 patients treated with continuous ambulatory peritoneal dialysis (CAPD) and 38 patients with chronic renal insufficiency (CHRI) not yet dialyzed. PAPP-A was measured by Time Resolved Amplified Cryptate Emission technology. Determination of AOPP is based on a spectrophotometric method.

RESULTS

PAPP-A levels are statistically significantly elevated in the both groups of dialyzed patients in comparison with healthy subjects (27.0 +/- 16.5 mIU/l in HD and 14.07 +/- 6.73 mIU/l in CAPD vs. 8.22 +/- 2.7 mIU/l in the control group, p < 0.0001 and p < 0.001, respectively, p < 0.05 HD vs. CAPD). The mean serum PAPP-A levels in the CHRI patients not yet dialyzed were not significantly higher in comparison with the control group (9.72 +/-4.44 vs. 8.22 +/- 2.7 mIU/l, n.s.). In the CHRI not dialyzed patients, we found a significant positive correlation between serum creatinine and PAPP-A levels (r = 0.68, p < 0.05). In comparison with controls, AOPP and CRP levels were significantly higher in HD patients [AOPP 155.0 +/- 37.9 micromol/l, p < 0.0001 vs. controls, CRP 10.0 (4.6- 26.9) mg/l (median, interquartile range), p < 0.0001 vs. controls], CAPD patients [AOPP 118.5 +/- 25.8 micromol/l, p < 0.0001 vs. controls, CRP 7.7 (2.0-18.8) mg/l, p < 0.01 vs. controls] and AOPP levels in chronic renal failure patients not yet dialyzed (98.5 +/- 43.24 micromol/l, p < 0.01 vs. controls). The correlations between PAPP-A and AOPP (r = 0.49, p < 0.05) and PAPP-A and CRP (r = 0.48, p < 0.05) serum concentration were statistically significant in HD patients. In CAPD patients, neither a correlation between PAPP-A and AOPP nor a correlation between PAPP-A and CRP were found.

CONCLUSION

We can conclude that serum PAPP-A levels sensitively reflect the changes in renal function, depend on dialysis modality, and may represent a novel marker associated with inflammation and oxidative stress in chronic renal failure patients.

Oxidative stress, inflammation and autoimmune reaction in type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) is associated with oxidative stress, elevation of inflammatory markers and other mechanisms, which may contribute to accelerated atherosclerosis. The aim of the study was to determine prominent factors of these pathogenic processes in patients with DM, to examine their relationship in serum, and to find out the differences between DM1 and DM2. Advanced oxidation protein products (AOPP), C-reactive protein (CRP), pregnancy-associated plasma protein-A (PAPP-A), anticardiolipin antibodies (ACA) and anti-beta2-glycoprotein-1 antibodies (anti-beta2-GPI) were determined in 27 patients with DM1, 27 patients with DM2 and 23 healthy subjects. AOPP, CRP and anti-beta2-GPI were significantly elevated in DM2 in comparison with healthy subjects (p<0.01, p<0.0001, p<0.0001, respectively). In DM1, anti-beta2-GPI were elevated (p<0.0001) as well, but there was no increase of either AOPP or CRP. There was no difference in PAPP-A levels in DM1 or DM2 and healthy subjects. In DM 1, AOPP correlate significantly with anti-beta2-GPI (r = 0.68, p<0.05). In DM2, there is a significant correlation between anti-beta2-GPI and PAPP-A (r=0.45, p<0.05). Oxidative stress and inflammation are more expressed in DM2 and they are partly related. In DM1, oxidative stress seems to be in closer link to autoimmune reaction than to inflammation.

Markers of inflammation in preeclampsia

Advanced oxidation protein products (AOPP) represent terminal products of proteins exposure to free radicals. The aim of this study was to estimate the serum AOPP levels in preeclamptic patients together with ultrasensitive C-reactive protein and anticardiolipin antibodies (ACA) IgG and IgM. 21 women in the third trimester of pregnancy were included in the study--10 women with preeclampsia and 11 women with normal outcome of pregnancy. AOPP levels in preeclampsia were higher than those in normal pregnant women in the third trimester, but not statistically significantly. The comparison with AOPP levels in non-pregnant women has shown a significant increase (P<0.0001). CRP in preeclampsia was significantly increased in comparison with third trimester levels in normal pregnancy (P<0.001) as well as with non-pregnant women (P<0.0001). In preeclampsia, the ACA IgG levels were even significantly lower than in normal pregnant women in the same gestation age, but significantly higher than in non-pregnant women (P<0.001). No difference was found in ACA IgM in preeclampsia and normal third trimester pregnancy and non-pregnant women. A statistically significant negative correlation was found between AOPP and ACA IgG (r= - 0.708, P<0.05). The results indicate enhanced oxidative and inflammatory reaction of maternal organism to pregnancy, which is more pronounced in preeclampsia than in uncomplicated pregnancy.

[Levels of advanced oxidation protein products (AOPP) in the first trimester of pregnancy]

Advanced oxidation protein products (AOPP) may be sensitive biomarkers for protein damage mediated by reactive oxygen species. AOPP were measured in the serum of 41 pregnant women in the 8th-12th week of pregnancy. Parameters of prenatal screening in the first trimester (pregnancy-associated plasma protein A--PAPP-A and free beta human chorionic gonadotrophin--free beta HCG) and anticardiolipin antibodies (ACA) IgG and IgM were determined as well. A group of healthy blood donors--women and men was used for comparison. AOPP were determined spectrophotometrically according to Witko-Sarsat [24] (absorbance at 340 nm) and were expressed in chloramine units (mumol/l). Other analytes were determined by immunoanalytic methods. AOPP levels in pregnant women in the first trimester are significantly higher in comparison with blood donors--women (89.46 +/- 33.38 mumol/l vs 57.34 +/- 16.31 mumol/l, p < 0.0001) but there is no statistically significant difference between pregnant women and blood donors--men (89.46 +/- 33.38 mumol/l vs 78.60 +/- 44.01 mumol/l). AOPP level does not correlate either with the age of pregnant women or with the parameters of prenatal screening and ACA IgG and IgM. Higher levels of AOPP in the serum of pregnant women in comparison with women--blood donors may reflect an increase of oxidative stress in pregnancy.

[Advanced oxidation protein products in pregnancy]

OBJECTIVE

Pregnancy and mainly its complications are associated with increased oxidative stress. Advanced oxidation protein products (AOPP) can serve as one of its markers.

SETTING

First Institute of Medical Chemistry and Biochemistry and Institute for Clinical Biochemistry, First Medical Faculty, Charles University; Institute for Care of Mother and Child, Prague.

METHODS

Together with parameters of prenatal screening, AOPP were measured in the serum of 23 pregnant women in the 2nd trimester of pregnancy. A group of healthy blood donors--women and men was used for comparison. AOPP were determined spectrophotometrically according to Witko-Sarsat (absorbance at 340 nm) and are expressed in chloramin units (mumol/l).

RESULTS

Serum AOPP concentrations in pregnant women are significantly higher in comparison with blood donors--women (85.90 +/- 18.70 mumol/l vs 57.34 +/- 16.31 mumol/l, P < 0.0001) but there is no statistically significant difference between pregnant women and blood donors--men (85.90 +/- 18.70 mumol/l vs 78.60 +/- 44.01 mumol/l). AOPP level does not correlate either with the age of pregnant women or with the parameters of prenatal screening (human chorionic gonadotrophin--HCG, alpha-1-fetoprotein--AFP and trophoblast-specific--beta-1-glycoproteion--SP1).

CONCLUSION

AOPP as a marker of oxidative stress is increased in the serum of pregnant women in comparison with women--blood donors but is similar as in men--blood donors which supports the hypothesis of hormonal influence. Nevertheless, AOPP do not correlate with the parameters of prenatal screening (HCG, AFP and SP1).

Kinetic imaging of chlorophyll fluorescence using modulated light

Fluorometers that measure the kinetics of chlorophyll fluorescence have become invaluable tools for determining the photosynthetic performance of plants. Many of these instruments use high frequency modulated light to measure the rate, efficiency and regulation of photosynthesis. The technique is non-invasive and is effective under diverse environmental conditions. Recently, imaging fluorometers have been introduced that reveal variability in photosynthesis over the surface of a leaf or between individual plants. Most imaging instruments depend on continuous light or low frequency modulated light for fluorescence excitation, which imposes serious limitations on measurements of the fluorescence parameters, especially the minimum fluorescence (F(0)) and variable fluorescence (F(V)). Here, we describe a new instrument that combines the advantage of high frequency modulated light with two-dimensional imaging of chlorophyll fluorescence. The fluorometer produces dynamic images of chlorophyll fluorescence from leaves or plants, providing accurate mapping of F(0) and F(V), and non-photochemical quenching. A significant feature of the instrument is that it can record fluorescence images of leaves in daylight under field conditions.