Explicit and automatic ejection fraction assessment on 2D cardiac ultrasound

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): DESKi

Background

Left ventricular ejection fraction (EF) is a key parameter to assess cardiovascular functions in 2D cardiac ultrasound, but its manual assessment is time-consuming and subject to high inter and intra-observer variability.

Deep learning-based approaches have been proposed to automatically predict EF but can suffer from a lack of explainability and interpretability, which limit the trust of the clinician and prevent errors from being detected.

Purpose

In this context, we propose a fully automatic method to reliably evaluate the biplane left ventricular EF on 2D echocardiography while following the modified Simpson’s rule calculation steps to provide explicit details to clinicians.

Methods

A deep learning model based on U-Net architecture was trained on internal apical 4 and 2-chamber echocardiographic images to segment the left ventricle and locate the mitral valve. Predicted segmentations are then validated with a statistical shape model which detects potential failures that could impact the final EF evaluation. Finally, end-diastolic and end-systolic frames are identified thanks to a spline interpolated from the remaining LV segmentations’ areas, and the EF is estimated on all available cardiac cycles.

This approach was trained on a dataset of 783 patients. Its performances were evaluated on an internal dataset of 200 patients with a large diversity of EF and on an external openly available dataset containing 450 patients.

Results

On the internal dataset, EF assessment achieved a mean absolute error of 6.10% and a bias of 1.56 ± 7.58% using multiple cardiac cycles and removing failed segmentations. Regarding end-diastolic and end-systolic volumes, the mean absolute error was evaluated at 13.75mL and 10.70mL respectively. Segmentation performances were evaluated with the Dice and the Hausdorff distance, respectively at 0.92 ± 0.41 and 6.13 ± 2.9mm.

On the external dataset, the approach predicted EF with a mean absolute error of 5.39% and a bias of -0.74 ± 7.12%. The mean absolute error for end-diastolic volume was 15.40mL and for end-systolic volume 8.18mL.

Conclusions

Following the recommended guidelines, we proposed an end-to-end fully automatic approach achieving state-of-the-art performances in EF evaluation in 2D cardiac ultrasound while giving explicit details to the clinicians at each step of the assessment. Abstract Figure. End-to-end fully automatic approach

[Training simulation during the announcement of fetal malformation discovered on screening ultrasound: Results of a pilot study]

OBJECTIVES

Breaking bad news (BBN) to a pregnant woman with fetal abnormalities (FA) on ultrasound (US) examination is a challenge. Announcement technique influences patient reaction. Physicians receive little training in BBN. The simulation and using a BBN protocol as the English SPIKES protocol which guides the announcement consultation according to 6 steps (Setting Up, Perception, Invitation, Knowledge, Emotions and Empathy, Strategy and Summary) can be used for this teaching. The objective was to assess feasibility simulation scenarii of BBN for FA discovered during US and to evaluate the usefulness of SPIKES protocol in this situation.

METHODS

Two scenarios have been created combining US simulator (US Mentor, Symbionix®) with simulated patient (SP). Scenarii objectives were to diagnose FA and break it to SP. Checklist derived from SPIKES was fulfilled by two investigators thanks to video recording, the SP and every participant (residents, physicians, fetal medicine specialists [FMS]). Participants filled out survey about the usefulness of this exercise too.

RESULTS

Nine physicians (3 residents, 4 physicians, 2 FMS) produced 18 scenarii. Seventy-eight percent of physicians thought simulation was like real situation of BBN during US examination. Majority of participant (88%) found that this simulation training could help them to increase their ability to BBN and that it can be used to teach residents (89%) or physicians (100%). FMS had better SPIKES checklist than physicians (P<0,05).

CONCLUSION

Simulation scenario of BBN for FA discovered during US is feasible by combining US simulator and SP. SPIKES protocol can be useful but a validated checklist should be created.

[Absent or hypoplastic thymus: A marker for 22q11.2 microdeletion syndrome in case of polyhydramnios]

OBJECTIVES

In prenatal diagnosis of 22q11.2 microdeletion syndrome, without cardiac malformation or multiple associated congenital anomalies, we study the presence of polyhydramnios and its association with thymic dysgenesis.

MATERIALS AND METHODS

This was a multicenter retrospective observational study. It was performed in two multidisciplinary centers for prenatal diagnosis in the south of France between January 1, 2010 and June 30, 2013. Inclusion criteria were prenatal diagnosis of 22q11.2 deletion syndrome. We excluded from the study any fetus with cardiac malformation or multiple associated congenital anomalies.

RESULTS

During the inclusion period, eleven antenatal diagnoses of 22q11.2 microdeletion syndrome have been made. Six cases were excluded: 5 fetuses with cardiac malformation and one with multiple associated congenital anomalies. Therefore, five cases of isolated polyhydramnios were included. All 5 fetuses had a thymic dysgenesis: 3 had a thymic agenesis and 1 thymic hypoplasia diagnosed by sonography and 1 had a thymic agenesis diagnosed by retrospective reading of fetal MRI.

CONCLUSION

When faced with a polyhydramnios, the presence of a thymic dysgenesis should be search for by ultrasound screening and would alert to the possibility of a 22q11.2 microdeletion syndrome. The confirmation of this is diagnosis by amniocentesis would enable improved antenatal support for parents and would enable early implementation of the multidisciplinary neonatal care that is required to avoid serious complications of this syndrome.

Daytime CLOCK Dephosphorylation Is Controlled by STRIPAK Complexes in Drosophila

In the Drosophila circadian oscillator, the CLOCK/CYCLE complex activates transcription of period (per) and timeless (tim) in the evening. PER and TIM proteins then repress CLOCK (CLK) activity during the night. The pace of the oscillator depends upon post-translational regulation that affects both positive and negative components of the transcriptional loop. CLK protein is highly phosphorylated and inactive in the morning, whereas hypophosphorylated active forms are present in the evening. How this critical dephosphorylation step is mediated is unclear. We show here that two components of the STRIPAK complex, the CKA regulatory subunit of the PP2A phosphatase and its interacting protein STRIP, promote CLK dephosphorylation during the daytime. In contrast, the WDB regulatory PP2A subunit stabilizes CLK without affecting its phosphorylation state. Inhibition of the PP2A catalytic subunit and CKA downregulation affect daytime CLK similarly, suggesting that STRIPAK complexes are the main PP2A players in producing transcriptionally active hypophosphorylated CLK.

Adherence in severe asthma

Adherence in asthma is an important cause for concern. Although nearly 50% of asthma patients are considered poorly adherent to therapeutic advices, adherence is still difficult to assess, understand and improve despite major medical consequences. In this review, we revisited the literature of the last 10 years related to adherence in severe asthma. The concepts have changed and "compliance" is usually replaced by "adherence". Assessment of adherence is addressing ethical issues, but provides important insight into difficult-to-treat asthma. Different tools have been used but none is routinely recommended. Health-related outcomes (poor control, exacerbations, hospitalizations, lung function decline), which are clearly associated with severe asthma, are often worsened by non-adherence with consequences also on patient related outcomes (quality of life). The potential behaviour associated with non-adherence and all other related factors including easy-to-recognize psychological traits can help for patient's future management. Therapeutic educational interventions have been recognized with a scientifically proven efficiency even though evolution and improvements are needed. A multidisciplinary approach is required in severe asthma. Therapeutic adherence for a given patient is always a prerequisite to any other aspects when addressing severe asthma phenotypes. Severe asthma should be considered only in those who still experienced poor asthma outcomes despite optimal adherence. At a glance, poor adherence and severe asthma should be considered antinomic. Better understanding of the causes and customised management are potential future directions.

[Asthmatic emergencies: a psychosocial approach to behaviour of asthmatics]

Emergency department admissions for acute asthma often show that patients have failed to manage their disease well. Such admissions may reflect poor asthma control, as defined in the literature, often due to a lack of education and medical follow-up. If patient-centred education has been recognised as effective, what are the best locations and the best moments in the patient's disease history to provide this education? The French Guidelines (HAS) on therapeutic education suggested that education should take place in the emergency department. Moreover, the emergency department is a unique healthcare situation and opportunity for therapeutic education. In the emergency department, a better analysis and understanding of an asthmatic's health orientated behaviour by a psychosocial interview may improve the patient's decision making and lead to an appropriate education programme.

The clockwork orange Drosophila protein functions as both an activator and a repressor of clock gene expression

The Drosophila clock relies on transcriptional feedback loops that generate daily oscillations of the clock gene expression at mRNA and protein levels. In the evening, the CLOCK (CLK) and CYCLE (CYC) basic helix-loop-helix (bHLH) PAS-domain transcription factors activate the expression of the period (per) and timeless (tim) genes. Posttranslational modifications delay the accumulation of PER and TIM, which inhibit CLK/CYC activity in the late night. We show here that a null mutant of the clockwork orange (cwo) gene encoding a bHLH orange-domain putative transcription factor displays long-period activity rhythms. cwo loss of function increases cwo mRNA levels but reduces mRNA peak levels of the 4 described CLK/CYC targets, inducing an almost complete loss of their cycling. In addition, the absence of CWO induces alterations of PER and CLK phosphorylation cycles. Our results indicate that, in vivo, CWO modulates clock gene expression through both repressor and activator transcriptional functions.

The F-box protein slimb controls the levels of clock proteins period and timeless

The Drosophila circadian clock is driven by daily fluctuations of the proteins Period and Timeless, which associate in a complex and negatively regulate the transcription of their own genes. Protein phosphorylation has a central role in this feedback loop, by controlling Per stability in both cytoplasmic and nuclear compartments as well as Per/Tim nuclear transfer. However, the pathways regulating degradation of phosphorylated Per and Tim are unknown. Here we show that the product of the slimb (slmb) gene--a member of the F-box/WD40 protein family of the ubiquitin ligase SCF complex that targets phosphorylated proteins for degradation--is an essential component of the Drosophila circadian clock. slmb mutants are behaviourally arrhythmic, and can be rescued by targeted expression of Slmb in the clock neurons. In constant darkness, highly phosphorylated forms of the Per and Tim proteins are constitutively present in the mutants, indicating that the control of their cyclic degradation is impaired. Because levels of Per and Tim oscillate in slmb mutants maintained in light:dark conditions, light- and clock-controlled degradation of Per and Tim do not rely on the same mechanisms.

Expression of human dopamine beta-hydroxylase in mammalian cells infected by recombinant vaccinia virus. Mechanisms for membrane attachment

Dopamine beta-hydroxylase (DBH) is found in neurosecretory vesicles in both membrane-bound and soluble forms. We expressed various human DBH cDNAs in two mammalian cell lines, using the vaccinia virus expression system. The expression of a full-length DBH cDNA (DBH-f) reproduced the native DBH electrophoretic pattern and led to the synthesis of an active enzyme composed of two subunits of 77 and 73 kDa. In contrast, a truncated cDNA lacking the first ATG (DBH-t) generated a single band of 73 kDa. Analysis of mutated recombinant clones demonstrates that the two polypeptides do not result from the use of an alternative translation initiator codon. These results, combined with deglycosylation experiments, allow us to attribute the double band pattern to an optional cleavage of the signal peptide. When the NH2-terminal extremity is shortened, cleavage becomes obligatory, underlining the role of the first 14 amino acids in the regulation of the cleavage of the signal peptide. Subcellular analysis of recombinant DBH-t and DBH-f proteins indicates that DBH is anchored to the membrane by two distinct mechanisms; one of them is due to the non-removal of the signal peptide, whereas the second one is independent of the presence of the signal sequence. Moreover, quantification of the fractionation experiments suggests that the two modes of membrane attachment are additive.

Retinoic acid induces cholinergic differentiation of cultured newborn rat sympathetic neurons

Many studies provide evidence that retinoic acid (RA), an endogenous derivative of vitamin A, plays a role in the development of the nervous system. We now report that RA controls the neurotransmitter phenotype of post-mitotic rat sympathetic neurons in cell culture. RA added to the culture medium increased the specific activity of choline acetyltransferase (ChAT) and the level of acetylcholine (ACh). Concomitantly, RA reduced the specific activities of two catecholamine synthetic enzymes, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) and the level of norepinephrine (NE). After a 2 week treatment with 5 microM RA, ChAT was increased by 5-10 fold, whereas TH and DBH were decreased by 10-15 fold and 2-3 fold, respectively, as compared to sympathetic neurons grown in the absence of RA. The modulation of the activity of the three enzymes was dose-dependent and followed a similar time course. The decrease of TH expression was demonstrated to be due to a decreased number of TH molecules.

Analysis of the human dopamine beta-hydroxylase promoter: transcriptional induction by cyclic AMP

We have analyzed some functional aspects of the promoter of the human dopamine beta-hydroxylase (DBH) gene. A fragment of 1,247 bp directly 5' to the transcriptional start was progressively shortened, placed in front of a reporter gene, and tested in a human neuroblastoma cell line expressing DBH (SK-N-SH-TFM) and in a monkey kidney cell line (CV-1). A remarkably short region (267 bp), directly upstream from the transcription start, was sufficient to confer activity and tissue-specific expression. Furthermore, the expression of the DBH gene was shown to be inducible by cyclic AMP in SK-N-SH-TFM cells. This effect was demonstrated to occur at the transcriptional level, as shown by run-on assays, and was due to the presence of a near-consensus cyclic AMP-responsive element located in the untranscribed 5' regulatory region of the gene.

Amphiphilic and nonamphiphilic forms of bovine and human dopamine beta-hydroxylase

We show that human and bovine dopamine beta-hydroxylases (DBH) exist under three main molecular forms: a soluble nonamphiphilic form and two amphiphilic forms. Sedimentation in sucrose gradients and electrophoresis under nondenaturing conditions, by comparison with acetylcholinesterase (AChE), suggest that the three forms are tetramers of the DBH catalytic subunit and bind either no detergent, one detergent micelle, or two detergent micelles. By analogy with the Gna4 and Ga4 AChE forms, we propose to call the nonamphiphilic tetramer Dna4 and the amphiphilic tetramers Da4I and Da4II. In addition to the major tetrameric forms, DBH dimers occur as very minor species, both amphiphilic and nonamphiphilic. Reduction under nondenaturing conditions leads to a partial dissociation of tetramers into dimers, retaining their amphiphilic character. This suggests that the hydrophobic domain is not linked to the subunits through disulfide bonds. The two amphiphilic tetramers are insensitive to phosphatidylinositol phospholipase C, but may be converted into soluble DBH by proteolysis in a stepwise manner; Da4II----Da4I----Dna4. Incubation of soluble DBH with various phospholipids did not produce any amphiphilic form. Several bands corresponding to the catalytic subunits of bovine DBH were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but this multiplicity was not simply correlated with the amphiphilic character of the enzyme. In the case of human DBH, we observed two bands of 78 and 84 kDa. As previously reported by others, the presence of the heavy subunit characterizes the amphiphilic forms of the enzyme. We discuss the nature of the hydrophobic domain, which could be an uncleaved signal peptide, and the organization of the different amphiphilic and nonamphiphilic DBH forms. We present two models in which dimers may possess either one hydrophobic domain or two domains belonging to each subunit; in both cases, a single detergent micelle would be bound per dimer.

Molecular definition of the 11p15.5 region involved in Beckwith-Wiedemann syndrome and probably in predisposition to adrenocortical carcinoma

To define more precisely, in molecular terms, the region involved in Beckwith-Wiedemann syndrome (BWS), we have studied patients with BWS and a constitutional duplication of 11p15 using eight 11p15 markers. In the first case with a de novo duplication and extra material on 11p, the region spanning pter to CALCA, excluded, was duplicated. In the second case, the rearrangement was characterized using somatic cell hybrids established with lymphocytes from the father who carried a balanced translocation t(11;18)(p15.4;p11.1). The breakpoint lay exactly in the same region. It could thus be inferred that the two sons, who were the first cases reported of BWS with dup11p15 and adrenocortical carcinoma (ADCC), carried a duplication similar to that observed in the first case. Together with evidence for specific somatic chromosomal events leading to loss of 11p15 alleles in familial cases of ADCC, it can be hypothesized that a gene involved in predisposition to ADCC maps to region 11p15.5.

Predicted amino acid sequence of bovine tyrosine hydroxylase and its similarity to tyrosine hydroxylases from other species

The previously obtained cDNAs coding for bovine tyrosine hydroxylase (TH) mRNA (mRNATH) were further analyzed, and the entire nucleotide sequence was determined. The mRNATH consists of 1,706 nucleotides with an open reading frame for 491 amino acids, which corresponds to a calculated molecular weight of 55,011. The predicted amino acid sequence of bovine TH is compared with that of rat TH and shows a similarity of 66% in the amino terminal (amino acids 1-157) and 91% in the carboxy terminal (amino acids 158-491) region of the TH protein molecule. The carboxy terminal region has been shown to make up the catalytic site of TH and, therefore, is conserved to a greater extent in different species than the amino terminal region, which has been shown to be mainly responsible for the regulation of the catalytic activity of TH. Three of the four serine residues (Ser 8, 19, and 40) that have been shown to be substrates for various protein kinases in rat TH are also present in bovine TH and are located near the amino terminal end of the molecule. The amino acids from position 60 to position 66 of rat TH are not present in bovine TH, resulting in the absence of a predicted hydrophobic region as compared with rat TH. This difference could result in an altered degree of regulation by posttranslational phosphorylation and also association to cell organelle membranes of bovine TH as compared with rat TH.

Cloning of quail tyrosine hydroxylase: amino acid homology with other hydroxylases discloses functional domains

A cDNA clone containing the entire coding region of quail tyrosine hydroxylase (TH) has been isolated and analyzed. Comparison with rat and human THs and phenylalanine hydroxylases reveals several highly conserved domains. Two of them, shared by all these hydroxylases, are localized in the central and C-terminal parts of the molecules, and most probably include the active site. Two others are found only in the TH molecules. One contains putative sites of phosphorylation and is implicated in the posttranslational regulation of the enzyme. The second highly preserved domain, consisting of a stretch of 21 amino acids, is presumably associated with an important feature of the enzyme that remains to be identified.

Localization of the human dopamine beta hydroxylase (DBH) gene to chromosome 9q34

A human cDNA clone for dopamine beta hydroxylase (DBH) has been isolated from a phaeochromocytoma library. In situ hybridization of this probe to replication-banded chromosomes has localized the gene to chromosome 9q34. The structural gene for the enzyme is therefore close to the ABO blood group locus. This suggests that the previously described activity variation in levels of serum DBH may reflect alterations in either the structure or regulation of the DBH coding sequences. Both biochemical and genetic evidence therefore indicate independence of DBH from the pterin-dependent aromatic amino acid hydroxylases of the neurotransmitter pathways.

The primary structure of human dopamine-beta-hydroxylase: insights into the relationship between the soluble and the membrane-bound forms of the enzyme

A full length dopamine-beta-hydroxylase (DBH) cDNA clone was isolated from a human pheochromocytoma lambda gt11 library. Both structural and functional evidence confirms the authenticity of the clone: (i) antibodies selected with fusion proteins generated by positive clones precipitate DBH activity, (ii) the sequence of three internal DBH tryptic peptides are included in the deduced DBH sequence, (iii) the previously reported N-terminal 15 amino acids of bovine DBH exhibits a nearly complete identity with that predicted for human DBH. The polypeptide chain of DBH comprises 578 amino acids corresponding to an unmodified protein of 64 862 daltons and is preceded by a cleaved signal peptide of 25 residues. DBH exists in both membrane-bound and soluble forms. The hydropathy plot reveals no obvious hydrophobic segment, except the signal peptide. S1 mapping analysis indicates no diversity in the 5' and 3' extremities of the DBH mRNA. Taken together with available biochemical data, these observations suggest that the membrane attachment of DBH probably results from a post-translational modification, glypiation being the most likely candidate. Comparative amino acid sequence analysis establishes that DBH shares no homology with the other catecholamine synthesizing enzymes, tyrosine hydroxylase and phenylethanolamine-N-methyl transferase.

Influence of cell-cell contact on levels of tyrosine hydroxylase in cultured bovine adrenal chromaffin cells

We have studied the regulation of tyrosine hydroxylase by cell-cell contact in primary cultures of bovine adrenal chromaffin cells. Preparation of dissociated chromaffin cells from bovine adrenal medullae or the harvesting of cultured cells resulted in a rapid decrease of the specific mRNA(TH) (defined as the amount of mRNA(TH) (where TH represents tyrosine hydroxylase) per microgram of total RNA). The decrease in mRNA(TH) levels appears to be stimulated by the loss of cell contact, as it occurs much more rapidly than would be expected from the turnover rate of mRNA(TH) in cultured cells. Similarly an enhanced rate of tyrosine hydroxylase enzyme degradation was observed in chromaffin cells when brought into low contact cultures. In contrast to the decrease in mRNA(TH) levels, however, the decrease in tyrosine hydroxylase enzyme levels was not so rapid and could be prevented in high contact cultures. The mRNA(TH) increased 4-fold in high contact cultures relative to dissociated cells within 1 day after plating. Similarly the rate of synthesis of tyrosine hydroxylase enzyme molecules was maximal after 1 day, although the increase in the absolute amount of tyrosine hydroxylase occurred only slowly. The increase in specific mRNA(TH) by cell contact was inhibited by alpha-amanitin, indicating that cell contact evokes an increase in tyrosine hydroxylase levels by increasing the transcription of mRNA(TH), in addition to inhibiting the degradation of tyrosine hydroxylase molecules.

The primary structure of human secretogranin I (chromogranin B): comparison with chromogranin A reveals homologous terminal domains and a large intervening variable region

We have determined and analyzed the primary structure of human secretogranin I (chromogranin B), a tyrosine-sulfated secretory protein found in a wide variety of peptidergic endocrine cells. A 2.5-kb cDNA clone, hybridizing to an mRNA of similar length, was isolated from a cDNA library of human pheochromocytoma. The identity of the clone was established by comparison of its deduced amino acid sequence with N-terminal and several internal secretogranin I sequences as well as by immunoprecipitation of the protein produced by in vitro transcription-translation of the cloned cDNA. Secretogranin I is a 657 amino acid long polypeptide of 76 kd and is preceded by a cleaved N-terminal signal peptide of 20 residues. Comparison of the predicted amino acid sequence of human secretogranin I with that of bovine chromogranin A reveals significant homologies near the N termini and at the C termini. The N-terminal homologous domains contain the only two cysteine residues of both proteins and form disulfide-stabilized loop structures. The sequences between the homologous terminal domains in both proteins differ but are characterized by a remarkable hydrophilicity, an abundance of acidic amino acids and potential dibasic cleavage sites for the generation of smaller, perhaps hormone-like, peptides.

A single human gene encoding multiple tyrosine hydroxylases with different predicted functional characteristics

Catecholaminergic systems in discrete regions of the brain are thought to be important in affective psychoses, learning and memory, reinforcement and sleep-wake cycle regulation. Tyrosine hydroxylase (TH) is the first enzyme in the pathway of catecholamine synthesis. Its importance is reflected in the diversity of the mechanisms that have been described which control its activity; TH levels vary both during development and as a function of the activity of the nervous system. Recently, we deduced the complete amino-acid sequence of rat TH from a complementary DNA clone encoding a functional enzyme. Here we demonstrate that, in man, TH molecules are encoded by at least three distinct messenger RNAs. The expression of these mRNAs varies in different parts of the nervous system. The sequence differences observed are confined to the 5' termini of the messengers and involve alternative splicing events. This variation has clear functional consequences for each putative form of the enzyme and could represent a novel means of regulating catecholamine levels in normal and pathological neurons.

Molecular genetics of catecholamines as an approach to the biochemistry of manic-depression

Manic depressive illness has been clearly established to exhibit a strong genetic component and is therefore amenable to linkage analysis using random DNA markers. In view of the catecholamine hypothesis of this disorder, the gene encoding tyrosine hydroxylase (TH) the limiting enzyme in catecholamines is a good candidate to investigate. This gene has been localized to chromosome 11 in close linkage with Harvey-ras-1. The various transcriptional and post-transcriptional mechanisms that modulate short and long-term TH activity are discussed. Human tyrosine hydroxylase is coded by at least three distinct mRNAs derived from a single gene. This variation has clear functional consequences and could represent a novel mode of regulating catecholamines levels in normal and pathological neurons.

Time course of the changes of TH mRNA in rat brain and adrenal medulla after a single injection of reserpine

A single injection of reserpine causes a long lasting enhancement of the activity of tyrosine hydroxylase (TH), the enzyme catalyzing the rate-limiting step in the biosynthesis of catecholamines. A sensitive method has been developed to assay both TH mRNA level and enzyme activity in tissue from a single rat. The time course of the induction was analysed in adrenals, locus coeruleus and substantia nigra. In both locus coeruleus and adrenals reserpine caused respectively 4.2- and 4.5-fold increase of TH mRNA which was maximal 2 days after drug injection. This increase is about twice that of the enzyme activity. No change was observed in substantia nigra. The effect lasted longer in locus coeruleus than in adrenal. In the latter, TH mRNA had almost returned to initial values at day 4 whereas at this time it is 3-fold higher in locus coeruleus and still significant at day 18. This result suggests that induction of TH results from an enhanced transcription of the TH gene. The time course difference between locus coeruleus and adrenals is most likely to result from a difference in the stability of TH mRNA in the two structures.

Localization of the human tyrosine hydroxylase gene to 11p15: gene duplication and evolution of metabolic pathways

Phenylalanine hydroxylase (PAH) and tyrosine hydroxylase (TH) are consecutive enzymes in the metabolic pathway leading to the production of catecholamine neurotransmitters. A comparison of recently available sequence data of these enzymes in the rat indicates about 70% homology in the 3' coding regions. We have localized TH by in situ hybridization to human chromosome region 11p15. Consideration of this assignment and that of PAH to chromosome 12, together with the known distribution of other pairs of related genes on these two chromosomes, provides convincing evidence of their ancestral relationship and suggests a role for gene duplication in the diversification of metabolic pathways in the vertebrate ancestors of mammals.

Cloning and sequence analysis of the cDNA encoding a snake neurotoxin precursor

A recombinant plasmid has been constructed containing a sequence of 186 nucleotides encoding a potent neurotoxin found in the venom of the sea-snake Laticauda semifasciata and designated as erabutoxin a. This sequence is flanked, in the upstream region, by a sequence of 60 nucleotides encoding a hydrophobic peptide fragment presumably involved in the secretion process of the neurotoxin. The sequence coding for the toxin ends with a termination codon which is followed by a 3'-untranslated sequence of approximately 240 nucleotides (excluding the poly(A) tract).

Complete coding sequence of rat tyrosine hydroxylase mRNA

Several clones specific for tyrosine hydroxylase [tyrosine 3-monooxygenase, L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] have been identified from a rat PC12 library by using the previously characterized clone pTH-1. The most complete of these, pTH-51, is 1758 base pairs long and covers most of the length of the mRNA, including the entire coding and 3' untranslated region. The polypeptide has an estimated molecular weight of 55,903 and some of its characteristic features are discussed.

Assignment of the human tyrosine hydroxylase gene to chromosome 11

Using a panel of human-mouse somatic cell hydrids and a cDNA probe for human tyrosine hydroxylase, we have assigned the structural gene for tyrosine hydroxylase to chromosome 11 by Southern blotting techniques.

Identification of cDNA clones coding for rat tyrosine hydroxylase antigen

Five recombinant DNA plasmids have been constructed that contain structural gene sequences for rat tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2]. Rat pheochromocytoma PC 12 cell line, which contains relatively high levels of catecholamine-synthesizing enzymes, was used to purify RNA. TyrOHase cDNA clones were identified by screening 350 cDNA clones constructed from partially purified TyrOHase mRNA. A rapid and powerful screening of the recombinant clones by differential colony hybridization was possible because TyrOHase is a tissue-specific protein. The final selection relied on the ability of cDNA inserts to hybridize specifically to TyrOHase mRNA as judged by cell-free translation and immunoprecipitation. Blot hybridization analysis of polyadenylylated RNA from PC 12 cells indicated a major mRNA species of 1.9 kilobases. A species of the same size was identified from a human pheochromocytoma tumor, indicating a crossreactivity between rat TyrOHase cDNA and human TyrOHase mRNA.