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M Brueckner

Publications and source records attributed to M Brueckner.

18 recordsLinked to original sources
PubMed2001

Cilia propel the embryo in the right direction.

Cilia have long been suspected to play a role in the determination of left-right asymmetry. Humans with the dominantly inherited condition Kartagener syndrome have defective cilia and a 50% incidence of mirror-image positioning of their organs (situs inversus). Analysis of mouse mutations affecting ciliary biogenesis and motility has demonstrated that the molecular motors kinesin and dynein are required to establish normal handed organismal asymmetry. The cilia that propel formation of the embryonic left-right axis are not conventional cilia, but monocilia. They are found on the node, or organizer, of the gastrulation-stage mouse embryo where they drive net leftward movement of the fluid surrounding the node, and initiate left-right asymmetry.

Animals↗
PubMed2000

Molecular motors: the driving force behind mammalian left-right development.

The molecular motors dynein and kinesin are large protein complexes that convert the energy generated by ATP hydrolysis into directional movement along the microtubule cytoskeleton. They are required for a myriad of cellular processes, including mitotic spindle movement, axonal and vesicular transport, and ciliary beating. Recently, it has been shown that, in addition, they have a unique role during embryonic patterning: they are required to orient and establish the left-right axis in early vertebrate development.

Animals↗
PubMed2000

Of mice and men: dissecting the genetic pathway that controls left-right asymmetry in mice and humans.

The increasing ability to manipulate the mouse genetically has created a model system that is both accessible and an accurate mirror of human development. A combination of analysis of existing spontaneous mouse mutations and creation of targeted mutations has identified at least z24 genes involved in the specification of mouse left-right asymmetry. These genes function in a carefully orchestrated manner first to create asymmetry at the node, then to signal it to the immediately surrounding cells via the node monocilia, and finally to amplify the initial asymmetry and propagate it to the developing organs. Defects at different steps in this pathway result in differences in the final phenotype. Human homologues exist for most of the mouse left-right determining genes. Notably, when human mutations in these genes have been identified in patients with defects of laterality determination, the human phenotype correlates very closely with the corresponding mouse phenotype.

Abnormalities, Multiple↗
PubMed1999

GATA4 haploinsufficiency in patients with interstitial deletion of chromosome region 8p23.1 and congenital heart disease.

Previous studies have shown that patients with deletion of distal human chromosome arm 8p may have congenital heart disease and other physical anomalies. The gene encoding GATA-4, a zinc finger transcription factor implicated in cardiac gene expression and development, localizes to chromosome region 8p23.1. To examine whether GATA-4 deficiency is present in patients with monosomy of 8p23.1 with congenital heart disease, we performed fluorescence in situ hybridization (FISH) with a GATA4 probe on cells from a series of patients with interstitial deletion of 8p23.1. Four individuals with del(8)(p23.1) and congenital heart disease were found to be haploinsufficient at the GATA4 locus by FISH. The GATA4 gene was not deleted in a fifth patient with del(8)(p23.1) who lacked cardiac anomalies. FISH analysis on cells from 48 individuals with congenital heart disease and normal karyotypes failed to detect any submicroscopic deletions at the GATA4 locus. We conclude that haploinsufficiency at the GATA4 locus is often seen in patients with del(8)(p23.1) and congenital heart disease. Based on these findings and recent studies showing that haploinsufficiency for other cardiac transcription factor genes (e.g., TBX5, NKX2-5) causes congenital heart disease, we postulate that GATA-4 deficiency may contribute to the phenotype of patients with monosomy of 8p23.1.

Adult↗
PubMed1999

Targeted deletion of the ATP binding domain of left-right dynein confirms its role in specifying development of left-right asymmetries.

Vertebrates develop distinct asymmetries along the left-right axis, which are consistently aligned with the anteroposterior and dorsoventral axes. The mechanisms that direct this handed development of left-right asymmetries have been elusive, but recent studies of mutations that affect left-right development have shed light on the molecules involved. One molecule implicated in left-right specification is left-right dynein (LRD), a microtubule-based motor protein. In the LRD protein of the inversus viscerum (iv) mouse, there is a single amino acid difference at a conserved position, and the lrd gene is one of many genes deleted in the legless (lgl) mutation. Both iv and lgl mice display randomized left-right development. Here we extend the analysis of the lrd gene at the levels of sequence, expression and function. The complete coding sequence of the lrd gene confirms its classification as an axonemal, or ciliary, dynein. Expression of lrd in the node at embryonic day 7.5 is shown to be symmetric. At embryonic day 8.0, however, a striking asymmetric expression pattern is observed in all three germ layers of the developing headfold, suggesting roles in both the establishment and maintenance of left-right asymmetries. At later times, expression of lrd is also observed in the developing floorplate, gut and limbs. These results suggest function for LRD protein in both ciliated and non-ciliated cells, despite its sequence classification as axonemal. In addition, a targeted mutation of lrd was generated that deletes the part of the protein required for ATP binding, and hence motor function. The resulting left-right phenotype, randomization of laterality, is identical to that of iv and lgl mutants. Gross defects in ciliary structure were not observed in lrd/lrd mutants. Strikingly, however, the monocilia on mutant embryonic node cells were immotile. These results prove the identity of the iv and lrd genes. Further, they argue that LRD motor function, and resulting nodal monocilia movement, are required for normal left-right development.

Adenosine Triphosphate↗
PubMed1998

Handed asymmetry in the mouse: understanding how things go right (or left) by studying how they go wrong.

All vertebrates have characteristic asymmetries along the left/right axis. The positioning of asymmetric visceral organs is highly conserved evolutionarily and disruptions in left/right patterning can lead to severe morphological defects, demonstrating the importance of regulation of left/right developmental asymmetries. Our understanding of vertebrate left/right pattern formation has been advanced by studying several mouse mutations which disrupt this process. These mutant mice have served as tools to help us to unravel the genetic pathways of left/right development. The identification and analysis of genes with asymmetric expression patterns has allowed us to begin to understand the mechanisms which regulate left/right development.

Animals↗
PubMed1997

Mutation of an axonemal dynein affects left-right asymmetry in inversus viscerum mice.

The development of characteristic visceral asymmetries along the left-right (LR) axis in an initially bilaterally symmetrical embryo is an essential feature of vertebrate patterning. The allelic mouse mutations inversus viscerum (iv) and legless (lgl) produce LR inversion, or situs inversus, in half of live-born homozygotes. This suggests that the iv gene product drives correct LR determination, and in its absence this process is randomized. These mutations provide tools for studying the development of LR-handed asymmetry and provide mouse models of human lateralization defects. At the molecular level, the normally LR asymmetric expression patterns of nodal and lefty are randomized in iv/iv embryos, suggesting that iv functions early in the genetic hierarchy of LR specification. Here we report the positional cloning of an axonemal dynein heavy-chain gene, left/right-dynein (lrd), that is mutated in both lgl and iv. lrd is expressed in the node of the embryo at embryonic day 7.5, consistent with its having a role in LR development. Our findings indicate that dynein, a microtubule-based motor, is involved in the determination of LR-handed asymmetry and provide insight into the early molecular mechanisms of this process.

Amino Acid Sequence↗
PubMed1996

The genetics of left-right development and heterotaxia.

Looping of the primitive heart tube is one of the earliest and most crucial steps in cardiac morphogenesis. Cardiac looping is dependent on normal left-right development, and defects in left-right development result in both heterotaxia and complex congenital heart disease. Single gene defects result in the wide spectrum of heterotaxy phenotypes, and conversely, different gene defects result in similar heterotaxy phenotypes. Elucidation of the molecular-genetic mechanisms of left-right development will greatly increase our understanding of the etiology of this complex group of congenital heart defects.

Animals↗
PubMed1995

Isolation of murine telomere-proximal sequences by affinity capture and PCR.

We describe a method of selectively enriching for murine telomere-proximal sequences using affinity capture followed by PCR amplification. The telomeric fragments were selected from NotI-digested and lambda exonuclease-resected mouse genomic DNA by annealing to a biotinylated riboprobe containing multiple copies of the telomere repeat (TTAGGG)n. The resultant DNA-RNA hybrids were selectively retained on a matrix with covalently bound avidin. The captured DNA was then specifically released by ribonuclease action, and PCR amplification was performed using mouse repeat primers. The PCR products were cloned and used to screen a mouse genomic cosmid library, and the resultant cosmid clones were analyzed by fluorescence in situ hybridization. Ten of 70 clones analyzed gave telomere-proximal hybridization signals, indicating an at least 500-fold enrichment for telomere-proximal sequences.

Animals↗
PubMed1993

Intestinal rotation and fixation abnormalities in heterotaxia: early detection and management.

Intestinal rotation and fixation abnormalities (IRFA) are known to coexist with heterotaxia (defined as an abnormal arrangement of body organs that is different from complete situs solitus or complete situs inversus), but little is known about the incidence of this association or its clinical management. We have reviewed the records of 34 patients diagnosed with heterotaxia during a 12-year period at Yale-New Haven Hospital in order to develop a plan for the early diagnosis of IRFA and to assess the value of preventive treatment in this complicated group of patients. Of the 34 patients with heterotaxia, all except one presented with complex congenital heart disease. The 34 patients were divided into two groups on the basis of their gastrointestinal workup for suspected IRFA. The 28 patients in group A had no upper gastrointestinal (GI) contrast study performed prior to symptoms suggestive of IRFA. Four of these 28 patients (14%) eventually developed complications of IRFA requiring emergency surgery. Group B consisted of six patients seen during the past 5 years with heterotaxia who had upper GI contrast studies while asymptomatic. All six (100%) were shown to have IRFA and subsequently underwent an uncomplicated elective Ladd procedure once their cardiac condition stabilized. This study confirms the high incidence of IRFA in patients with heterotaxia. We propose that evaluating patients with heterotaxia syndrome for IRFA while asymptomatic may prevent the need for emergency abdominal surgery in patients that have major cardiovascular anomalies.

Abnormalities, Multiple↗
PubMed1992

Duplication/deficiency mapping of situs inversus viscerum (iv), a gene that determines left-right asymmetry in the mouse.

A recessive mutation in the mouse, situs inversus viscerum (iv), results in randomization of organ position along the left-right body axis: approximately 50% of the progeny of homozygous matings exhibit situs solitus and 50% exhibit situs inversus. Recent studies have established genetic linkage between iv and the immunoglobulin heavy chain gene complex (Igh-C), located on distal mouse chromosome 12. In the present study, we have refined the genetic map location of iv relative to the breakpoint of a reciprocal translocation, T(5;12)31H, involving the telomeric region of chromosome 12 distal to Igh-C and the proximal region of chromosome 5. The translocation results in a large 12(5) derivative chromosome and a small 5(12) derivative chromosome. Because mice with either monosomy or tertiary trisomy for the 5(12) chromosomal region are viable, duplication/deficiency mapping is possible. Deficiency mapping was performed by mating iv/iv homozygotes and T31H heterozygotes. Two animals monosomic for distal mouse chromosome 12 were produced. One of the animals with cytogenetically confirmed monosomy for distal chromosome 12 exhibited situs inversus, indicating that the iv mutation is located at or distal to the T31H breakpoint. For duplication analysis, matings were initially carried out between iv/iv homozygotes and unbalanced T31H animals trisomic for distal chromosome 12. Cytogenetically verified tertiary trisomic progeny were identified and backcrossed with iv/iv homozygotes. The resulting trisomic progeny, 50% of which are expected to carry the iv mutation on both cytogenetically normal copies of chromosome 12, were scored for phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Neonatal correction of transposition of the great arteries: the Connecticut experience.

The treatment of transposition of the great arteries, a common congenital cardiac defect, has undergone significant development. Prior to 1989 a surgical approach which repaired the transposition at the atrial level (Senning's operation), but did not restore normal anatomy, was the procedure of choice. Since 1989 a surgical approach that restores normal anatomy (Jatene's arterial switch) has been followed. Forty-four patients have been corrected since 1979 (N = 26 Senning's operation, N = 18 arterial switch). The arterial switch patients are corrected at an earlier age, have a longer, more complex operation without a significant increase in operative mortality, intensive care, or duration of hospitalization. The prevalence or frequency of normal ventricular function and normal sinus rhythm is significantly increased over the repair at the atrial level. The frequency of pulmonary stenosis is increased. The duration of follow-up for these patients is significantly shorter than for those with atrial level repair.

Connecticut↗
PubMed1991

Establishment of left-right asymmetry in vertebrates: genetically distinct steps are involved.

Vertebrates exhibit a characteristic pattern of asymmetrical positioning of the visceral organs along the left-right axis. A remarkable developmental step establishes this pattern--primitive organs migrate from symmetrical midline positions of origin into lateral positions. The first organ to pursue such movement is the cardiac tube, which forms a rightward 'D' loop; other organs follow concordantly. The signals and mechanisms directing such organ migration can be studied by analysis of heritable defects of humans and mice. In general, these defects behave as loss-of-function mutations that lead to random determination of visceral situs: for an affected embryo there is an equal chance of correct situs or situs inversus. Distinct phenotypes and patterns of inheritance of these defects suggest that at least three genes are involved in left-right determination, apparently members of a developmental pathway. These genes should be amenable to molecular analysis. We are studying a recessive allele of the mouse called inversus viscerum (iv). Using linkage analysis with cloned restriction fragment length polymorphism markers, we have genetically mapped the iv gene to the distal portion of mouse chromosome 12. We are now pursuing isolation of the gene using methods of positional cloning. Analysis of the iv gene product and of its site and timing of expression may offer clues to how left-right lateralization occurs.

Animals↗
PubMed1990

ESWL and gallstone dissolution with MTBE via a naso-vesicular catheter.

Endoscopic placement of a naso-vesicular catheter was successful in 90% (45/50) of patients with cholecystolithiasis. The first 7 patients were treated by MTBE dissolution alone. Dissolution was discontinued after a maximum of 14 days, as only two patients were rendered stone free. In one patient, 3 tiny pigment stones were sucked out through the catheter, and in another inoperable patient a pigtail endoprosthesis was finally inserted into the gallbladder. In the remaining 36 patients, combined ESWL and MTBE dissolution therapy was carried out. Treatment was broken off by one patient after one week, and interrupted in another due to catheter dislodgement. After an average of 10 days with 1-9 ESWL sessions (average: 3) complete stone clearance was achieved in 60% (20/34) of patients. Fourteen of the patients who completed treatment, and the one with catheter dislodgement still have sludge in the gallbladder, which is being treated with oral bile acids. The procedure-related complication rate was 10% (3 pancreatitis, 1 cystic duct perforation and 1 guidewire impaction). The mortality rate was zero. There was no evident complication due to either ESWL or MTBE dissolution.

Catheterization↗
PubMed1989

Linkage mapping of a mouse gene, iv, that controls left-right asymmetry of the heart and viscera.

Inherited single gene defects have been identified in both humans and mice that lead to loss of developmental control over the left-right asymmetry of the heart and viscera. In mice the recessively inherited mutation iv leads to such apparent loss of control over situs: 50% of iv/iv mice exhibit situs inversus and 50% exhibit normal situs. The affected gene product has not been identified in these animals. To study the normal function of iv, we have taken an approach directed to the gene itself. As a first step, we have mapped iv genetically, by examining its segregation in backcrosses with respect to markers defined by restriction fragment length polymorphisms. The iv locus lies 3 centimorgans (cM) from the immunoglobulin heavy-chain constant-region gene complex (Igh-C) on chromosome 12. A multilocus map of the region suggests the gene order centromere-Aat (alpha 1-antitrypsin gene complex)-(11 cM)-iv-(3 cM)-Igh-C-(1 cM)-Igh-V (immunoglobulin heavy-chain variable-region gene complex).

Animals↗
PubMedDate not supplied

A comparison between surgical, endoscopic and percutaneous management of pancreatic pseudocysts--long term results.

In a retrospective study, the data of 127 patients who had been treated in our hospital between 1985 and 1990 for pancreatic pseudocysts were re-examined and analysed in order to evaluate the therapeutic success. In 13 cases (10%), a spontaneous regression was observed. Forty-four patients (35%) were treated surgically, 37 (29%) were managed endoscopically and 7 (6%) received a percutaneous treatment. The remaining 26 patients (20%) had received a combined form of therapy either primarily or later within the course of their treatment. After an average period of 33 months, 97 patients could be either re-questioned or re-examined. The results showed that 50% of the patients treated surgically and 52% of those treated endoscopically were without complaints. The over-all mortality rate was 9%. A lack of success following various therapeutic regimes resulted in up to 20% of all patients. In summary, endoscopic drainage proved to be a simple method with a low complication rate and an alternative to internal surgical drainage particularly for persistent alcoholics and patients over 65 years of age. Endoscopic drainage is not an alternative for patients with persistent abdominal pain symptoms or complications.

Adult↗