Nonsense mutation in TITF1 in a Portuguese family with benign hereditary chorea

Differential diagnosis of Huntington's disease- neurological aspects of NKX2-1-related disorders

Benign hereditary chorea (BHC) is an inherited neurological disorder consisting of childhood-onset, nonprogressive chorea, generally without any other manifestations. In most reported cases, the inheritance of BHC is autosomal dominant but both incomplete penetrance and variable expressivity are observed and can be caused by NKX2-1 mutations. The spectrum contains choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress syndrome. The neurological symptoms can be misdiagnosed as Huntington's disease (HD). The two Polish families were diagnosed with NKX2-1 gene mutations and a literature review concerning the NKX2-1-related disorders was conducted. All family members were examined by experienced movement disorders specialists. PubMed database was searched to obtain previously described NKX2-1 cases. Whole exome sequencing (WES) was performed in one proband (Family A) and direct NKX2-1 sequencing in the second (Family B). Two Polish families were diagnosed with NKX2-1 gene mutations (p.Trp208Leu and p.Cys117Alafs*8). In one family, the co-occurrence of HD was reported. Forty-nine publications were included in the literature review and symptoms of 195 patients with confirmed NKX2-1 mutation were analyzed. The most common symptoms were chorea and choreiform movements, and delayed motor milestones. The NKX2-1 mutation should always be considered as a potential diagnosis in families with chorea, even with a family history of HD. Lack of chorea does not exclude the NKX2-1-related disorders.

Altered pituitary morphology as a sign of benign hereditary chorea caused by TITF1/NKX2.1 mutations

Benign hereditary chorea (BHC) is a rare genetically heterogeneous movement disorder, in which conventional neuroimaging has been reported as normal in most cases. Cystic pituitary abnormalities and features of empty sella have been described in only 7 patients with BHC to date. We present 4 patients from 2 families with a BHC phenotype, 3 of whom underwent targeted pituitary MR imaging and genetic testing. All four patients in the two families displayed a classic BHC phenotype. The targeted pituitary MR imaging demonstrated abnormal pituitary sella morphology. Genetic testing was performed in three patients, and showed mutations causing BHC in three of the patients, as well as identifying a novel nonsense mutation of the TITF1/NKX2-1 gene in one of the patients. The presence of the abnormal pituitary sella in two affected members of the same family supports the hypothesis that this sign is a distinct feature of the BHC phenotype spectrum due to mutations in the TITF1 gene. Interestingly, these abnormalities seem to develop in adult life and are progressive. They occur in at least 26% of patients affected with Brain-lung-thyroid syndrome. As a part of the management of these patients we recommend to perform follow-up MRI brain with dedicated pituitary imaging also in adult life as the abnormality can occur years after the onset of chorea.

Chiari Malformation Type I in a Patient with a Novel NKX2-1 Mutation

Chiari Malformation Type 1 is a congenital, condition characterized by abnormally shaped cerebellar tonsils that are displaced below the level of the foramen magnum. NKX2-1 gene encodes a transcription factor expressed during early development of thyroid, lung, and forebrain, and germline NKX2-1 mutations can lead to dysfunction in any of these three organs, resulting in brain-lung-thyroid syndrome. There have been few reports of structural brain anomalies in patients with an NKX2-1-related disorder. We report the first case of a girl with a genetically identified mutation in NKX2-1 that presents with a Chiari Malformation Type 1, eventually expanding the phenotypic spectrum of NKX2-1-related disorders while also highlighting a novel heterozygous pathogenic variant at exon 3 that disrupts the reading framework, originating an NKX2-1 protein with a different C-terminal.

Is Benign Hereditary Chorea Really Benign? Brain-Lung-Thyroid Syndrome Caused by NKX2-1 Mutations

BACKGROUND

Since its localization to the NKX2-1 gene in 2002, the phenotype of the disorder historically called "benign hereditary chorea" has been expanding beyond chorea.

METHODS

The phenomenology of movement disorders and other symptomatology associated with mutations in NKX2-1 were characterized after a detailed evaluation of consecutive patients evaluated in our clinic over the past 3 years.

RESULTS

We studied 5 patients (3 females), ages 2 to 31 years, with confirmed pathogenic variants in NKX2-1. All patients exhibited chorea, gross motor delay, and gait impairment. Other symptoms included neonatal respiratory failure (n = 4), cognitive deficits (n = 3), hypothyroidism (n = 4), joint laxity (n = 2), myoclonus (n = 1), hypotonia (n = 3), and seizures (n = 1). Chorea often proved refractory to medical therapies.

CONCLUSIONS

The phenotype associated with pathogenic variants in NKX2-1 frequently includes disabling and often medically refractory neurological and non-neurological abnormalities. We therefore suggest that the term benign hereditary chorea be abandoned in favor of its genetic designation as NKX2-1-related disorder.

Novel Imaging Biomarkers for Huntington's Disease and Other Hereditary Choreas

PURPOSE OF THE REVIEW

Imaging biomarkers for neurodegenerative disorders are primarily developed with the goal to aid diagnosis, to monitor disease progression, and to assess the efficacy of disease-modifying therapies in support to clinical outcomes that may either show limited sensitivity or need extended time for their evaluation. This article will review the most recent concepts and findings in the field of neuroimaging applied to Huntington's disease and Huntington-like syndromes. Emphasis will be given to the discussion of potential pharmacodynamic biomarkers for clinical trials in Huntington's disease (HD) and of neuroimaging tools that can be used as diagnostic biomarkers in HD-like syndromes.

RECENT FINDINGS

Several magnetic resonance (MR) and positron emission tomography (PET) molecular imaging tools have been identified as potential pharmacodynamic biomarkers and others are in the pipeline after preclinical validation. MRI and 18F-fluorodeoxyglucose PET can be considered useful supportive diagnostic tools for the differentiation of other HD-like syndromes. New trials in HD have the primary goal to lower mutant huntingtin (mHTT) protein levels in the brain in order to reduce or alter the progression of the disease. MR and PET molecular imaging markers have been developed as tools to monitor disease progression and to evaluate treatment outcomes of disease-modifying trials in HD. These markers could be used alone or in combination for detecting structural and pharmacodynamic changes potentially associated with the lowering of mHTT.

Benign Hereditary Chorea: An Update

Benign hereditary chorea (BHC) is a childhood-onset, hyperkinetic movement disorder normally with little progression of motor symptoms into adult life. The disorder is caused by mutations to the NKX2.1 (TITF1) gene and also forms part of the “brain–lung–thyroid syndrome”, in which additional developmental abnormalities of lung and thyroid tissue are observed. In this review, we summarize the main clinical findings in “classical” BHC syndrome and discuss more recently reported atypical features, including non-choreiform movement phenotypes. We highlight additional non-motor characteristics such as cognitive impairment and psychiatric symptoms, while discussing the evidence for BHC as a developmental disorder involving impaired neural migration and other multisystem developmental abnormalities. Finally, we will discuss the efficacy of available therapies in both affected pediatric and adult cohorts. Delineation of the BHC disease spectrum will no doubt expand our understanding of this disorder, facilitating better targeting of genetic testing and establish a framework for future clinical trials.

NKX2.1-Related Disorders: a novel mutation with mild clinical presentation

Background

A highly variable phenotype characterized by thyroid, respiratory and neurological defects has been reported in an already established group of disorders namely NKX2.1-related disorders. We describe here the case of an infant with a novel mutation of the NKX2.1 gene characterized by mild clinical presentation.

Aim of the study was to elucidate the genotype-phenotype correlation in our patient.

Methods

We performed genetic analysis of the NKX2.1 gene in an infant with no neonatal respiratory distress and near-normal results at neonatal screening test for congenital hypothyroidism, choreoathetosis, ataxia and delayed independent walking.

Results

A novel mutation of the NKX2.1 gene has been identified, that is responsible for a mild framework of congenital hypothyroidism and neurological symptoms.

Conclusions

The frequency of congenital hypothyroidism cases associated with NKX2.1 mutations is expected to be higher in a subgroup of patients, selected according to the neurological presentation. In these patients the analysis of NKX2.1 mutational status is recommended.

A novel de novo mutation of the TITF1/NKX2-1 gene causing ataxia, benign hereditary chorea, hypothyroidism and a pituitary mass in a UK family and review of the literature

Benign hereditary chorea (BHC) is a rare autosomal dominant condition characterized by early onset, non-progressive chorea, usually caused by mutations in the thyroid transcription factor-1 gene (TITF1). We describe a novel mutation arising de novo in a proband presenting in infancy with delayed walking and ataxia. She later developed chorea, then hypothyroidism and a large cystic pituitary mass. Her daughter presented in infancy with delayed walking and ataxia and went on to develop non-progressive chorea and a hormonally inactive cystic pituitary mass. Mutational analysis of the whole coding region of the TITF1 gene was undertaken and compared with a population study of 160 control subjects. This showed that both affected subjects have a heterozygous A > T substitution at nucleotide 727 of the TITF1 gene changing lysine to a stop codon at residue 211. Genetic analysis of parents and siblings of the proband confirmed that the mutation arose de novo in the proband. The mutated lysine is an evolutionarily highly conserved amino acid in the protein homoeodomain (HD) where most point mutations associated with BHC are located. The range of mutations in BHC is reviewed with particular emphasis on pituitary abnormalities. Cystic pituitary masses and abnormalities of the sella turcica are reported in just 6.4 % of published cases. This is a new nonsense mutation associated with ataxia, benign chorea and pituitary abnormalities which further extends the phenotype of this condition. Mutational screening of TITF1 is important in cases of sporadic or dominant juvenile-onset ataxia, with mild chorea where no other cause is found, particularly if pituitary abnormalities are seen on imaging.

Benign hereditary chorea: a case report and brief review of inherited choreas

BACKGROUND

Chorea as a nonprogressive abnormality is often associated with Sydenham chorea in the pediatric population. Benign hereditary chorea is a condition where chorea presents before age 5 years and runs a very slowly progressive course.

PATIENTS

We present a family that was thought to have a variant of Huntington disease but on genetic testing was confirmed to have benign hereditary chorea. We describe a 7-year-old girl in this family who presented with involuntary movements and hyperactivity.

RESULTS

Our family was determined to have benign hereditary chorea after extensive genetic testing and follow-up.

CONCLUSIONS

When chorea presents as a familial entity, the differential diagnosis is limited and is often misdiagnosed as Huntington disease. In this family benign hereditary chorea was found to be the cause.

Comprehensive genotyping and clinical characterisation reveal 27 novel NKX2-1 mutations and expand the phenotypic spectrum

BACKGROUND

NKX2-1 encodes a transcription factor with large impact on the development of brain, lung and thyroid. Germline mutations of NKX2-1 can lead to dysfunction and malformations of these organs. Starting from the largest coherent collection of patients with a suspected phenotype to date, we systematically evaluated frequency, quality and spectrum of phenotypic consequences of NKX2-1 mutations.

METHODS

After identifying mutations by Sanger sequencing and array CGH, we comprehensively reanalysed the phenotype of affected patients and their relatives. We employed electrophoretic mobility shift assay (EMSA) to detect alterations of NKX2-1 DNA binding. Gene expression was monitored by means of in situ hybridisation and compared with the expression level of MBIP, a candidate gene presumably involved in the disorders and closely located in close genomic proximity to NKX2-1.

RESULTS

Within 101 index patients, we detected 17 point mutations and 10 deletions. Neurological symptoms were the most consistent finding (100%), followed by lung affection (78%) and thyroidal dysfunction (75%). Novel symptoms associated with NKX2-1 mutations comprise abnormal height, bouts of fever and cardiac septum defects. In contrast to previous reports, our data suggest that missense mutations in the homeodomain of NKX2-1 not necessarily modify its DNA binding capacity and that this specific type of mutations may be associated with mild pulmonary phenotypes such as asthma. Two deletions did not include NKX2-1, but MBIP, whose expression spatially and temporarily coincides with NKX2-1 in early murine development.

CONCLUSIONS

The high incidence of NKX2-1 mutations strongly recommends the routine screen for mutations in patients with corresponding symptoms. However, this analysis should not be confined to the exonic sequence alone, but should take advantage of affordable NGS technology to expand the target to adjacent regulatory sequences and the NKX2-1 interactome in order to maximise the yield of this diagnostic effort.

The molecular causes of thyroid dysgenesis: a systematic review

BACKGROUND

Congenital hypothyroidism (CH) is a frequent disease occurring with an incidence of about 1/2500 newborns/year. In 80-85% of the cases CH is caused by alterations in thyroid morphogenesis, generally indicated by the term "thyroid dysgenesis" (TD). TD is generally a sporadic disease, but in about 5% of the cases a genetic origin has been demonstrated. In these cases, mutations in genes playing a role during thyroid morphogenesis (NKX2-1, PAX8, FOXE1, NKX2-5, TSHR) have been reported.

AIM

This work reviews the main steps of thyroid morphogenesis and all the genetic alterations associated with TD and published in the literature.

Identification and functional characterization of a novel mutation in the NKX2-1 gene: comparison with the data in the literature

BACKGROUND

NKX2-1 mutations have been described in several patients with primary congenital hypothyroidism, respiratory distress, and benign hereditary chorea, which are classical manifestations of the brain-thyroid-lung syndrome (BTLS).

METHODS

The NKX2-1 gene was sequenced in the members of a Brazilian family with clinical features of BTLS, and a novel monoallelic mutation was identified in the affected patients. We introduced the mutation in an expression vector for the functional characterization by transfection experiments using both thyroidal and lung-specific promoters.

RESULTS

The mutation is a deletion of a cytosine at position 834 (ref. sequence NM_003317) (c.493delC) that causes a frameshift with formation of an abnormal protein from amino acid 165 and a premature stop at position 196. The last amino acid of the nuclear localization signal, the whole homeodomain, and the carboxy-terminus of NKX2-1 are all missing in the mutant protein, which has a premature stop codon at position 196 (p.Arg165Glyfs*32). The p.Arg165Glyfs*32 mutant does not bind DNA, and it is unable to transactivate the thyroglobulin (Tg) and the surfactant protein-C (SP-C) promoters. Interestingly, a dose-dependent dominant negative effect of the p.Arg165Glyfs*32 was demonstrated only on the Tg promoter, but not on the SP-C promoter. This effect was also noticed when the mutation was tested in presence of PAX8 or cofactors that synergize with NKX2-1 (P300 and TAZ). The functional effect was also compared with the data present in the literature and demonstrated that, so far, it is very difficult to establish a specific correlation among NKX2-1 mutations, their functional consequence, and the clinical phenotype of affected patients, thus suggesting that the detailed mechanisms of transcriptional regulation still remain unclear.

CONCLUSIONS

We describe a novel NKX2-1 mutation and demonstrate that haploinsufficiency may not be the only explanation for BTLS. Our results indicate that NKX2-1 activity is also finely regulated in a tissue-specific manner, and additional studies are required to better understand the complexities of genotype-phenotype correlations in the NKX2-1 deficiency syndrome.

Benign hereditary chorea: dopaminergic brain imaging in patients with a novel intronic NKX2.1 gene mutation

Mutations in the NKX2.1 gene, which is essential for the development, differentiation and organization of the basal ganglia, cause benign hereditary chorea (BHC) characterized by childhood-onset non-progressive chorea. We herein report the clinical features of six patients from a single family with a novel intronic mutation and present the dopaminergic neuronal imaging by using positron emission tomography (PET) imaging to assess the integrity of the striatal dopaminergic system using [(11)C]-CFT for the presynaptic dopamine transporter function and [(11)C]-raclopride for the postsynaptic D2 receptor function. The patients showed mild generalized chorea without either congenital hypothyroidism or a history of pulmonary infection and some of the patients had goiter. Genetic analyses of NKX2.1 gene showed a novel heterozygous c.464-9C>A mutation that created a new acceptor splice site resulting in the production of an aberrant transcript with a 7-bp insertion identical to a intronic sequence of genomic DNA. Oral levodopa failed to improve the involuntary movement, while haloperidol, a dopamine D2 receptor blocking agent, exacerbated the choric movement in a single patient. The dopaminergic PET studies in the two patients revealed decreased raclopride binding in the striatum, while the CFT binding was not altered. The impairment of D2 receptor function in the basal ganglia may result in exacerbation of the chorea induced by haloperidol. The molecular brain imaging and therapeutic response may help elucidate the pathophysiological mechanism of the motor control in the BHC-associated NKX2.1 mutation.

TITF-1 gene mutation in a case of sporadic non-progressive chorea. Response to levodopa treatment

Benign hereditary chorea (BHC) is a rare autosomal dominant disorder characterized by non-progressive chorea of early onset, without other underlying progressive neurologic dysfunction. Hypothyroidism and pulmonary problems may also be associated. Recently, mutations in the thyroid transcription factor 1 gene (TITF-1), linked to chromosome 14q, have been related to this disorder. We describe the clinical phenotype and response to levodopa treatment in a 6 year-old girl affected with sporadic non-progressive chorea, and a de novo TITF-1 gene mutation, in order to increase understanding of this rare and misdiagnosed disorder.

Hypoperfusion in caudate nuclei in patients with brain-lung-thyroid syndrome

Mutations in NKX2-1 cause neurological, pulmonary, and thyroid hormone impairment. Recently, the disease was named brain-lung-thyroid syndrome. Here, we report three patients with brain-lung-thyroid syndrome. All patients were unable to walk until 24 months of age, and still have a staggering gait, without mental retardation. They have also had choreoathetosis since early infancy. Genetic analysis of NKX2-1 revealed a novel missense mutation (p.Val205Phe) in two patients who were cousins and their maternal families, and a novel 2.6-Mb deletion including NKX2-1 on chromosome 14 in the other patient. Congenital hypothyroidism was not detected on neonatal screening in the patient with the missense mutation, and frequent respiratory infections were observed in the patient with the deletion in NKX2-1. Oral levodopa did not improve the gait disturbance or involuntary movement. The results of (99m)Tc-ECD single-photon emission computed tomography (ECD-SPECT) analyzed using the easy Z-score imaging system showed decreased cerebral blood flow in the bilateral basal ganglia, especially in the caudate nuclei, in all three patients, but no brain magnetic resonance imaging (MRI) abnormalities. These brain nuclear image findings indicate that NKX2-1 haploinsufficiency causes dysfunction of the basal ganglia, especially the caudate nuclei, resulting in choreoathetosis and gait disturbance in this disease.

The integrity of cholinergic basal forebrain neurons depends on expression of Nkx2-1

The transcription factor Nkx2-1 belongs to the homeobox-encoding family of proteins that have essential functions in prenatal brain development. Nkx2-1 is required for the specification of cortical interneurons and several neuronal subtypes of the ventral forebrain. Moreover, this transcription factor is involved in migratory processes by regulating the expression of guidance molecules. Interestingly, Nkx2-1 expression was recently detected in the mouse brain at postnatal stages. Using two transgenic mouse lines that allow prenatal or postnatal cell type-specific deletion of Nkx2-1, we show that continuous expression of the transcription factor is essential for the maturation and maintenance of cholinergic basal forebrain neurons in mice. Notably, prenatal deletion of Nkx2-1 in GAD67-expressing neurons leads to a nearly complete loss of cholinergic neurons and parvalbumin-containing GABAergic neurons in the basal forebrain. We also show that postnatal mutation of Nkx2-1 in choline acetyltransferase-expressing cells causes a striking reduction in their number. These degenerative changes are accompanied by partial denervation of their target structures and results in a discrete impairment of spatial memory.

A novel nonsense mutation in the TITF-1 gene in a Japanese family with benign hereditary chorea

A Japanese family with a novel nonsense mutation in the TITF-1 gene (p.Y98X) is described. The proband showed severe generalized chorea, delayed motor development, subnormal intelligence, congenital hypothyroidism, bronchial asthma, and a history of pulmonary infection, all of which are characteristic features of Brain-Thyroid-Lung syndrome. On the other hand, her brother and mother showed a mild benign hereditary chorea (BHC) phenotype with congenital hypothyroidism. Intrafamilial phenotypic variation is common in BHC/Brain-Thyroid-Lung syndrome and suggests the existence of other genetic or environmental factors regulating TITF-1 function. Although choreic movement in BHC/Brain-Thyroid-Lung syndrome is recognized as non-progressive, the proband showed re-exacerbation of choreic movement at puberty. The dopamine agonist, ropinirole hydrochloride, reduced her choreic movements, suggesting that levodopa and/or dopamine agonists may compensate for underdeveloped dopaminergic pathways in this disorder.

Benign hereditary chorea: an update

Benign hereditary chorea (BHC, MIM 118700) is a rare autosomal dominant disorder manifesting with chorea in conjunction with hypothyroidism and respiratory problems, a triad also named "brain-lung-thyroid syndrome". BHC is characterized by childhood onset with minimal or no progression into adult life and normal cognitive function. The genetic basis of BHC has been partially resolved, when mutations in the TTF1 gene on chromosome 14q13 encoding the thyroid transcription factor-1 have been identified in a number of BHC patients, suggesting that aberration of TTF1 transcriptional function or haploinsufficiency is associated with this disorder. TTF1 (also known as TITF1, TEBP or NKX2-1), belonging to the NKX2 homeodomain transcription factor family, has been implicated in several important molecular pathways essential for brain, thyroid and lung morphogenesis. Clinical evaluation of TTF1 gene mutations carrier patients exposed the involvement of each of the triad's components characterized by heterogeneity between index cases and even within families. This review highlights the current updates on expanded clinical aspects of BHC, imaging and treatment experience, its genetic markers, proposed molecular mechanisms, animal models and link to cancer.

Myoclonus-dystonia syndrome

Myoclonus dystonia syndrome (MDS) refers to a group of heterogeneous nondegenerative clinical conditions characterized by the association of myoclonus and dystonia as the only or prominent symptom. The "core" of MDS is represented by inherited myoclonus-dystonia (M-D), a disorder with autosomal-dominant inheritance and reduced penetrance, beginning in early childhood with a relatively benign course, with myoclonus as the most predominant and disabling symptom. Alcohol responsiveness and psychiatric symptoms are characteristic features. Mutations in the epsilon-sarcoglycan gene (SGCE, DYT11) represent the major genetic cause, but M-D is genetically heterogeneous. In a variable proportion of M-D patients no mutation is found, and at least one other locus (DYT15) has been linked to the disease. Patients with primary dystonia, with or without the DYT1 mutation, may show irregular and arrhythmic jerky movements associated with dystonia. Usually dystonia is the prominent symptom and the myoclonic jerk involves the same body region; this condition, currently defined as "myoclonic dystonia," is included in the spectrum of MDS. Dopa-responsive dystonia due to mutation in the GTP-CH gene and vitamin E deficiency can present with a phenotype of dystonia and myoclonus in combination; both conditions should be considered in the diagnostic approach to patients since they are potentially treatable.

Genetic Basis of Children's Interstitial Lung Disease

Specific genetic causes for children's interstitial lung disease (chILD) have been identified within the past decade. These include deletions of or mutations in genes encoding proteins important in surfactant production and function (SP-B, SP-C, and ABCA3), surfactant catabolism (GM-CSF receptor), as well as transcription factors important for surfactant production (TTF1) or lung development (Fox F1), with heterozygous deletions or loss-of-function mutations of the latter resulting in alveolar capillary dysplasia (ACD) with misalignment of the pulmonary veins. Familial pulmonary fibrosis in adults may result from mutations in genes encoding components of telomerase and SP-A2. While not yet reported in children, the expression of these genes in alveolar type II epithelial cells supports a key role for the disruption of normal homeostasis in this cell type in the pathogenesis of interstitial lung disease. The identification of specific genetic causes for chILD now allows for the possibility of non-invasive diagnosis, and provides insight into basic cellular mechanisms that may allow the development of novel therapies.

Ongoing expression of Nkx2.1 in the postnatal mouse forebrain: potential for understanding NKX2.1 haploinsufficiency in humans?

Coordinated movements require the caudate-putamen and the globus pallidus, two nuclei belonging to the basal ganglia, to be intact and functioning properly. Many neurons populating these regions derive from the medial ganglionic eminence, a transient structure that expresses the transcription factor Nkx2.1 during prenatal development. Accordingly, the basal ganglia of Nkx2.1(-/-) mice are heavily affected and a substantial loss of several types of GABAergic interneurons has been observed. Interestingly, heterozygous mutation of the NKX2.1 gene in humans has been described as causing an unusual disorder from the second year of life onwards, which is mainly characterized by disturbances of motor abilities and delayed speech development. In the present study, we therefore investigated whether Nkx2.1 is still expressed in the young adult and aged mouse forebrain. After birth, the most intense immunolabeling for Nkx2.1 was detected in several components of the hypothalamic region, in the subventricular zone of the ventral tips lining the lateral ventricles, and in neighboring structures including the striatum, the globus pallidus and the various nuclei of the septal complex. Surprisingly, this staining pattern was substantially maintained into adulthood. Double immunocytochemistry for Nkx2.1 and various neuronal markers revealed that mainly parvalbumin-containing GABAergic neurons, but also cholinergic neurons, of the ventral forebrain express this protein. Moreover, in situ hybridization confirmed that these neurons maintain synthesis of Nkx2.1 throughout life. The robust expression of Nkx2.1 by these neurons points to a broad functional spectrum within the adult forebrain.

Five new TTF1/NKX2.1 mutations in brain-lung-thyroid syndrome: rescue by PAX8 synergism in one case

Thyroid transcription factor 1 (NKX2-1/TITF1) mutations cause brain-lung-thyroid syndrome, characterized by congenital hypothyroidism (CH), infant respiratory distress syndrome (IRDS) and benign hereditary chorea (BHC). The objectives of the present study were (i) detection of NKX2-1 mutations in patients with CH associated with pneumopathy and/or BHC, (ii) functional analysis of new mutations in vitro and (iii) description of the phenotypic spectrum of brain-lung-thyroid syndrome. We identified three new heterozygous missense mutations (L176V, P202L, Q210P), a splice site mutation (376-2A-->G), and one deletion of NKX2-1 at 14q13. Functional analysis of the three missense mutations revealed loss of transactivation capacity on the human thyroglobulin enhancer/promoter. Interestingly, we showed that deficient transcriptional activity of NKX2-1-P202L was completely rescued by cotransfected PAX8-WT, whereas the synergistic effect was abolished by L176V and Q210P. The clinical spectrum of 6 own and 40 published patients with NKX2-1 mutations ranged from the complete triad of brain-lung-thyroid syndrome (50%), brain and thyroid disease (30%), to isolated BHC (13%). Thyroid morphology was normal (55%) and compensated hypothyroidism occurred in 61%. Lung disease occurred in 54% of patients (IRDS at term 76%; recurrent pulmonary infections 24%). On follow-up, 20% developed severe chronic interstitial lung disease, and 16% died. In conclusion, we describe five new NKX2.1 mutations with, for the first time, complete rescue by PAX8 of the deficient transactivating capacity in one case. Additionally, our review shows that the majority of affected patients display neurological and/or thyroidal problems and that, although less frequent, lung disease is responsible for a considerable mortality.

Mutation of a gene for thyroid transcription factor-1 (TITF1) in a patient with clinical features of resistance to thyrotropin

Resistance to TSH (RTSH [MIM 275200]) is a heterogeneous condition defined by variable degree of insensitivity to biologically active TSH. While this condition is classically caused by loss-of-function mutations of the TSH receptor gene (TSHR), several patients have exhibited RTSH-like phenotype in the apparent absence of TSHR mutations, and some of them have mutations of PAX8 or GNAS1. We identified a Japanese boy with congenital hypothyroidism who suffered from recurrent lower respiratory infection during infancy and choreoathetosis at a later age. At 14 years of age, he was diagnosed as having RTSH, on the basis of compensated hypothyroidism (TSH, 30.2 mU/L; FT4, 1.2 ng/dl), disproportionate increments of thyroid hormones and TSH during a TRH test (DeltaFT3, 0.4 pg/ml; DeltaT3, 13 ng/dl; and DeltaTSH, 88.3 mU/L), and normal ultrasound thyroid image and radioactive iodine uptakes. Molecular analysis for TITF1 revealed a novel de novo heterozygous deletion/insertion mutation (c.470_479delinsGCG,) that is predicted to lose the entire homeodomain and the NK2-specific domain. We suggest that a heterozygous loss-of-function TITF1 mutation can also cause RTSH-compatible phenotype.

A novel NKX2.1 mutation in a family with hypothyroidism and benign hereditary chorea

BACKGROUND

We studied a boy with congenital hypothyroidism, benign hereditary chorea, and respiratory distress. His mother and his grandfather were affected by hypothyroidism with a late onset and benign hereditary chorea. The aim of this study was to establish the genetic defects that cause that phenotype and study the molecular mechanisms of the pathology.

METHODS

NKX2.1, PAX8, NKX2.5, and TAZ genes were sequenced.

RESULTS

Direct sequencing of the NKX2.1 gene showed, in all the affected, a new heterozygous mutation from cytosine to adenine in the second base of the triplet encoding for the amino acid at position 145. The mutation (C609A) is responsible for a change from serine to a stop codon (S145X). We also demonstrated that the mutant protein is predominantly in the cytoplasm and unable to translocate into the nucleus. Of note, the S145X mutation produces variable phenotypes in the affected members of the family. No mutations have been identified in the NKX2.5, PAX8, and TAZ genes.

CONCLUSIONS

Our study extends the knowledge of the functional effect of NKX2.1 mutations and further highlights the complexities of genotype-phenotype correlation in the NKX2.1 deficiency syndromes.

Benign hereditary chorea revisited: a journey to understanding

Benign hereditary chorea (BHC) has been characterized as an autosomal dominant disorder manifesting nonprogressive chorea without dementia. However, there has been controversy regarding its existence. Diagnosis has been based solely on clinical criteria with many patients and families demonstrating "atypical" features and until recently, no diagnostic test was available for confirmation. Since 2002, mutations in the thyroid transcription factor (TITF-1) gene have been identified as resulting in some cases of BHC. Additionally, the clinical spectrum has expanded to include abnormalities in thyroid and lung with the putative mechanism of disease resulting from gene haploinsufficiency and reduced protein product. This review summarizes both a historical perspective and our current understanding of BHC.

Clinical differentiation of genetically proven benign hereditary chorea and myoclonus-dystonia

Because of clinical similarities, benign hereditary chorea and myoclonus-dystonia (DYT11) might be confused. No systematic comparisons of genetically proven cases with thyroid transcription factor-1 (TITF-1) and epsilon-sarcoglycan (SGCE) mutations have been performed to date. Three index patients and one index patients' daughter underwent genetic analysis of the TITF-1 and the SGCE gene. The movement disorders of all patients were assessed by video review. A new splicing mutation (376-2A>C) of the TITF-1 gene was detected in a mother and her daughter. Two additional patients carried a de novo SGCE nonsense mutation in exon 3 (R97X) and a novel SGCE missense mutation in exon 6 (G227V). Both TITF-1 mutation carriers presented with infancy-onset, nonprogressive chorea, which responded to alcohol intake. In addition, dystonia of the neck and trunk as well as fleeting jerky movements of the distal limbs could be observed. The mutually exclusive appearance of lightning-like myoclonic jerks triggered by action in SGCE mutation carriers and of continuous chorea of all limbs in TITF-1 mutation carriers phenotypically discriminated both genetic disorders. TITF-1 mutations should be considered in choreiform movement disorders with onset in infancy even in the presence of dystonia and myoclonic jerks.

Mutational analysis of thyroid transcription factor-1 gene (TTF-1) in lung carcinomas

We studied the expression and mutation of thyroid transcription factor-1 (TTF-1) gene in 92 cases of lung carcinomas comprised of lung adenocarcinoma (36 cases), squamous cell lung carcinoma (42 cases), small cell lung carcinoma (8 cases), and large cell lung carcinoma (6 cases) to investigate whether TTF-1 gene mutation predisposed to the development of lung cancer. Normal lung tissues were obtained from each of the 92 patients. The tissues served as controls. Polymerase chain reaction-single-strand conformation polymorphism, denaturing high-performance liquid chromatography, and DNA sequencing were used to analyze TTF-1 gene mutation and its relationship with the carcinogenesis of lung cancer. We detected the expression of TTF-1 protein and messenger RNA (mRNA) in paraffin-embedded lung carcinomas and their normal lung tissues by tissue microarray. TTF-1 protein and mRNA intensities were measured by Leica-Q500 MC Image Analysis System to reveal their correlation with TTF-1 mutation in lung carcinomas. TTF-1 gene missense and synonymous mutation are present in lung carcinomas with the mutation rate of 16%. TTF-1 protein and mRNA are higher in normal lung tissues than in different lung carcinomas. TTF-1 gene mutation is correlated with the loss of TTF-1 protein and mRNA. The analyses of TTF-1 gene missense mutation and synonymous mutation and the loss of TTF-1 protein and mRNA can be regarded as the important indexes of molecular pathology of lung carcinoma.

Benign hereditary chorea: clinical, neuroimaging, and genetic findings

Benign hereditary chorea is an autosomal dominant disease with an early onset of symptoms. In some families, symptoms tend to decrease in adulthood, suggesting that the disorder results from a developmental disturbance in the brain. Individuals with benign hereditary chorea, a nonprogressive disease, have normal or slightly below normal intelligence. The locus for benign hereditary chorea is on chromosome 14. Benign hereditary chorea is a result of mutations in the thyroid transcription factor 1 gene. Previous neuroimaging and pathological investigations of the brain showed no notable abnormalities in patients with this condition. In this study, 5 patients from 1 family with typical clinical features of benign hereditary chorea are presented. Clinical severity varied considerably in the family. Brain magnetic resonance imaging results were normal. Brain single photon emission computed tomography in 3 children, performed 1 hour after intravenous injection of 0.35 mCi/kg of body weight of technetium 99m ethyl cysteinate dimer, showed markedly decreased uptake in the right striatum and the right thalamus in 1 child. The oldest child had mildly reduced uptake in the right putamen and the left thalamus. Brain single photon emission computed tomographic findings in the youngest child were normal. Contrary to other reports of radionuclide brain imaging, notable brain single photon emission computed tomography changes were detected in 2 of 5 patients. Brain single photon emission computed tomography findings did not seem to correlate with the clinical status of the children.

Functional characterization of a novel mutation in TITF-1 in a patient with benign hereditary chorea

Benign hereditary chorea (BHC) is an autosomal dominant disorder of early onset characterised by non progressive choreic movements with normal cognitive function occasionally associated with hypothyroidism and respiratory problems. Numerous pieces of evidence link BHC with TITF-1/NKX2.1 gene mutations. We studied a patient with a familial benign hereditary chorea and normal thyroid and respiratory function. Sequence analysis of TITF-1 revealed the presence of a heterozygous C>T substitution at nucleotide 532, predicted to change an arginine (CGA) with a stop codon (TGA) at position 178 (R178X). A functional analysis shows that the mutated TTF-1 is not binding DNA, nor activating the canonical thyroid target gene promoter or interfering with the ability of wild type TTF-1 to activate transcription. In addition, the mutated protein is predominantly cytoplasmic, rather than nuclear as in the case of the wild type TTF-1. Thus, we have identified a new mutation in the TTF-1 coding gene in a patient with benign hereditary chorea. The results show that the mutation leads to a haploinsufficiency of TITF-1 and opens the question of genotype/phenotype correlation.