A Missense Variant p.Ala117Ser in the Transthyretin Gene of a Han Chinese Family with Familial Amyloid Polyneuropathy

Identification of a novel transthyretin mutation D39Y in a cardiac amyloidosis patient and its biochemical characterizations

Hereditary transthyretin cardiac amyloidosis (hATTR-CA) is a rare autosomal dominantly inherited disease caused by mutations in the transthyretin (TTR) gene. TTR mutations often cause the instability of transthyretin, production of misfolded proteins, and ultimately excessive deposition of insoluble amyloid fibrils in the myocardium, thereby leading to cardiac dysfunction. Herein, we report a novel transthyretin D39Y mutation in a Chinese family. We characterized the kinetic and thermodynamic stabilities of D39Y mutant TTR, revealing that TTR D39Y mutant was less stable than WT TTR and more stable than amyloidogenic mutation TTR L55P. Meanwhile, the only FDA approved drug Tafamidis showed satisfactory inhibitory effect toward ATTR amyloid formation and strong binding affinity in test tube revealed by isothermal titration calorimetry. Finally, we measured the well-folded tetrameric TTR concentration in patient's and his descents' blood serum using a previously reported UPLC-based assay. Notably, the tetramer concentrations gradually increased from symptomatic D39Y gene carrier father, to asymptomatic D39Y gene carrier daughter, and further to wild type daughter, suggesting the decrease in functional tetrameric TTR concentration may serve as an indicator for disease age of onset in D39Y gene carriers. The study described a Chinese family with hATTR-CA due to the TTR variant D39Y with its destabilizing effect in both kinetic and thermodynamic stabilities.

Clinical phenotypes and genetic features of hereditary transthyretin amyloidosis patients in China

Background

Hereditary transthyretin amyloidosis (hATTR) is a progressive and fatal disease with heterogenous clinical presentations, limited diagnosis and poor prognosis. This retrospective analysis study aimed to report the genotypes and phenotypes of herediary transthyretin amyloidosis (hATTR) in Chinese through a systematic review of published literature.

Methods

The systematic review included structured searches of peer-reviewed literature published from 2007 to 2020 of following online reference databases: PubMed, Web of Science and the literature database in China. Extracted data included sample size, personal information (sex, age, natural course, family history), mutation type, clinical milestones and reason of death.

Results

We described 126 Chinese patients with hereditary transthyretin amyloidosis identified through a systematic review of 30 studies. The most common genotype in the Chinese population was Gly83Arg (25, 19.8%), which most likely presented visual and neurological abnormalities without reported death. The second and third most common genotypes were Val30Met (20, 15.9%) and Val30Ala (10, 7.9%). Peripheral neurological manifestations (91, 72%) were dominant in 126 patients. The followed manifestation was autonomic neurological abnormalities (73, 58%). Half of the cases were reported to have visual disorders, and nearly one-third of the cases presented cardiac abnormalities. Among all 126 reported patients, 46.03% were classified as neurological type, 30.16% as mixed type and only 2.38% as cardiac type. In addition. Chinese patients were mostly early onset, with age of onset at 41.8 (SD: 8.9) years, and the median time from onset to death was 7.5 [IQR: 5.3] years. Patients with cardiac involvement had a shorter survival duration (log Rank (Mantel-Cox), χ² = 26.885, P < 0.001).

Conclusions

This study focused on 126 Chinese hATTR patients obtained from a literature review. A total of 26 kinds of TTR mutations were found and the most common one was Gly83Arg. As for phenotype, 46.03% were classified as neurological type, 30.16% as mixed type and only 2.38% as cardiac type. Chinese hATTR patients were mostly early onset (AO 41.8 years), and the median time from onset to death was 7.5 years.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02481-9.

Ala97Ser transthyretin amyloidosis-associated polyneuropathy, clinical and neurophysiological profiles in a Thai cohort

Background

Ala97Ser transthyretin amyloidosis-associated polyneuropathy (ATTRA97S-PN) is a rare form of inherited polyneuropathy, usually manifesting with late-onset (> 50) progressive polyneuropathy. This mutation is mostly prevalent in Taiwanese and Han-Chinese individuals. The aim of this study was to describe the clinical and comprehensive neurophysiological profiles of ATTRA97S-PN in Thai patients.

Methods

The clinical profiles and serial neurophysiologic studies (nerve conduction study (NCS), quantitative sensory test (QST), and comprehensive autonomic function test (AFT)) of symptomatic ATTRA97S-PN patients who had been followed-up at King Chulalongkorn Memorial Hospital during 2010–2020 were retrospectively reviewed.

Results

Nine symptomatic patients (55.6 % were male) from four unrelated families were included. All were Thais of mixed Thai Chinese descent. The mean age of onset was 48.3 (32–60) years. The mean age at diagnosis was 54.8 (33–66) years. Three patients developed early-onset (< 40y) polyneuropathy. The mean Neuropathy Impairment Score was 41.33 (10–92) at diagnosis. Sensory (9/9) and autonomic (9/9) neuropathies were more frequent than motor neuropathy (5/9), which appeared in the late stage of disease. Hypoesthesia in the feet, and gastrointestinal autonomic symptoms were frequently reported as the initial symptoms. The course of neuropathy progressed over years to decades. The worsening of neuropathy tended to progress faster once motor nerves were affected in both clinical and neurophysiological aspects. Concurrent cardiac amyloidosis was found in 6/9 patients. NCS showed length-dependent sensorimotor axonal polyneuropathy in 5/9 patients, and median neuropathy at the wrist (mostly bilateral) in 7/9 patients. QST showed abnormalities in the vibratory detection threshold, the cold detection threshold and the heat pain sensation in 8/9, 8/9 and 7/7 tested patients, respectively. AFT results were abnormal in all. The mean composite autonomic severity score was 5 (3–9).

Conclusions

This clinical study is the first of ATTRA97S-PN in Thai patients. The mixed polyneuropathy-cardiopathy phenotype was the most common manifestation. In this cohort, the age of onset was lower, and the course of neuropathy was relatively longer, than that in previous studies. Some patients may develop early-onset polyneuropathy. This mutation has not yet been documented in any population other than Han Chinese-related populations, probably suggesting a founder effect. Further studies are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02243-3.

Hereditary transthyretin amyloidosis in mainland China: a unicentric retrospective study

OBJECTIVE

This study aims to report the genotypes and phenotypes of hereditary transthyretin amyloidosis (ATTR) in a large Chinese cohort, yet the clinical and genetic profiles of ATTR remain elusive in mainland China.

METHODS

Fifty-four patients with molecularly confirmed ATTR from 39 unrelated families were identified by sequencing the TTR gene. Sural nerve biopsies were performed in 40 of these cases. The clinical and electrophysiological data were retrospectively collected and analyzed.

RESULTS

The male/female ratio was 42:12. The average age of patients at the onset of the disease was 47.8 ± 13.0 years. The late-onset type occurred in 29 cases (53.7%). Twenty-two probands (56.4%) had a family history with ATTR. The initial symptoms were limb paresthesia in 33 cases (61.1%), autonomic dysfunction in 15 cases (27.8%), and blurred vision in 6 cases (11.1%). A total of 22 different TTR mutations were identified, including Val30Met (25.6%) in 10 families in North China and Ala97Ser in 4 families (10.3%) in South China. Electrophysiological studies revealed general sensorimotor axonal polyneuropathy in 33/44 cases (75.0%), mixed neuropathy with axonal and demyelinating impairment features in 9/44 cases (20.5%) and isolated carpal tunnel syndrome in two cases. Sural nerve biopsies revealed positive Congo red staining in 16/40 cases (40.0%).

CONCLUSION

Chinese patients with ATTR exhibited heterogeneous TTR genotypes and clinical phenotypes. Val30Met remains the most common mutation type in mainland China.

Extended Study of NUS1 Gene Variants in Parkinson's Disease

Parkinson's disease (PD), is the second most common neurodegenerative disorder worldwide. Genetic, environmental factors, and aging are its primary development contributors. Recently the nuclear undecaprenyl pyrophosphate synthase 1 homolog (Saccharomyces cerevisiae) gene (NUS1) was reported as a candidate gene for PD, which raised our interest in the relationship between NUS1 and PD. This study was aimed to further explore the role of NUS1 variants in PD development. Genetic analysis for 308 Han-Chinese PD patients and 308 ethnically matched controls using whole exome sequencing was conducted. Additionally, a total of 60 articles involving in whole exome/whole genome sequencing or direct sequencing of the NUS1 gene from PubMed database between July 1, 2011 and August 26, 2020 were reviewed to evaluate PD-associated NUS1 variants. No potentially pathogenic NUS1 variant was found in 308 PD cases, and no frequency biases between 308 PD cases and 308 controls were observed for the only non-synonymous variant p.Asp179Glu (genotype: χ² = 0.093, P = 0.761; allele: χ² = 0.092, P = 0.762). No pathogenic or disease-associated NUS1 variant was reported in the 5,636 PD cases of the 60 articles. In summary, current findings indicate that NUS1 variant is not a common genetic factor contributing to PD.

Corneal sub-basal whorl-like nerve plexus: a landmark for early and follow-up evaluation in transthyretin familial amyloid polyneuropathy

BACKGROUND AND PURPOSE

Small-fiber nerves are the first to be involved in transthyretin familial amyloid polyneuropathy (TTR-FAP) patients. In vivo corneal confocal microscopy (CCM) is a noninvasive technique to detect small-fiber polyneuropathy (SFN) by quantifying corneal nerve morphology. The characteristic whorl-like pattern of the corneal nerve provides a static landmark for observation. We aimed to evaluate whether CCM images of the whorl-like plexus can sensitively evaluate and monitor disease progression in FAP patients.

METHODS

Fifteen FAP patients and 15 controls underwent neurological evaluation and CCM observation. Corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD) detected by conventional method and inferior whorl length (IWL), inferior whorl fiber density (IWFD), and inferior whorl branch density (IWBD) were compared in controls and patients. The Langerhans cell (LC) density in each image was calculated.

RESULTS

All CCM parameters were significantly reduced with disease progression. Preclinical patients had significantly lower IWL (P = 0.008) than age-matched controls. IWL (P = 0.006), CNFL (P = 0.005), CNBD (P = 0.008), and CNFD (P = 0.014) were significantly lower in early-phase patients. LC density was significantly increased around the central whorl in early-phase patients and was relatively lower in progressive patients. Both IWL and CNFL correlated with the severity of neuropathy, and IWL was more significantly reduced. The area under the receiver operating characteristic (ROC) curve for FAP with CNFL and IWL was 88.0% (95% CI, 70.9%-96.9%) and 89.3% (95% CI, 72.6%-97.6%), respectively, exceeding other parameters.

CONCLUSIONS

IWL is a more sensitive surrogate to detect preclinical SFN in FAP and can best discriminate patients from controls. The clustering of immature LCs at the inferior whorl area might reflect the inflammatory response of small-fiber nerves at the early stage.

Identification of a CCDC114 variant in a Han-Chinese patient with situs inversus

The function and position of the internal organs within the human body are based on left-right (LR) asymmetry. Human LR asymmetry disorders are characterized by abnormal LR asymmetric arrangement of the internal organs resulting from defective embryonic nodal cilia and nodal signaling pathway. The coiled-coil domain containing 114 gene (CCDC114) is related to the biogenesis of cilia and attachment of the outer dynein arms (ODAs) to the axoneme of cilia. Mutations in the CCDC114 gene are reported to cause a subtype of primary ciliary dyskinesia (PCD) named ciliary dyskinesia, primary, 20 (CILD20). Patients with CCDC114 mutations present with a type of ciliopathy with high clinical heterogeneity. In the present study, a Han-Chinese patient with situs inversus was recruited. Exome sequencing was performed on this patient combined with variant validation by Sanger sequencing. A homozygous variant c.584T>C (p.L195P) in the CCDC114 gene was identified as the likely genetic cause for situs inversus in this patient. The findings of our study extend the mutational spectrum of the CCDC114 gene, and contribute to clarifying the pathogenesis of human ciliopathies and benefit genetic counseling.

Novel Compound Heterozygous PRKN Variants in a Han-Chinese Family with Early-Onset Parkinson's Disease

Genetic factors are thought to play an important role in the pathogenesis of Parkinson's disease (PD), particularly early-onset PD. The PRKN gene is the primary disease-causing gene for early-onset PD. The details of its functions remain unclear. This study identified novel compound heterozygous variants (p.T240K and p.L272R) of the PRKN gene in a Han-Chinese family with early-onset PD. This finding is helpful in the genetic diagnosis of PD and also the functional research of the PRKN gene.

A COL4A5 Missense Variant in a Han-Chinese Family with X-linked Alport Syndrome

BACKGROUND

Alport syndrome (AS) is an inherited familial nephropathy, characterized by progressive hematuric nephritis, bilateral sensorineural hypoacusis and ocular abnormalities. X-linked AS (XLAS) is the major AS form and is clinically heterogeneous, and it is associated with defects in the collagen type IV alpha 5 chain gene (COL4A5).

OBJECTIVE

The purpose of this research is to detect the genetic defect responsible for renal disorder in a 3-generation Han-Chinese pedigree.

METHODS

Detailed family history and clinical data of the family members were collected and recorded. Whole exome sequencing (WES) was applied in the proband to screen potential genetic variants, and then Sanger sequencing was used to verify the variant within the family. Two hundred unrelated ethnically matched normal individuals (male/female: 100/100, age 37.5 ± 5.5 years) without renal disorder were recruited as controls.

RESULTS

Three patients (I:1, II:1 and II:2) presented microscopic hematuria and proteinuria, and the patient I:1 developed uremia and end stage renal disease (ESRD) by age 55 and showed sensorineural hearing loss. Patient II:2 developed mild left ear hearing loss. Cataracts were present in patients I:1 and II:1. A COL4A5 gene missense variant, c.2156G>A (p.G719E), located in the Gly-X-Y repeats of exon 28, was identified to co-segregate with the renal disorder in this family. The variant was absent in 200 ethnically matched controls.

CONCLUSION

By conducting WES and Sanger sequencing, a COL4A5 missense variant, c.2156G>A (p.G719E), was identified to co-segregate with the renal disorder, and it is possible that this variant is the genetic cause of the disorder in this family. Our study may extend the mutation spectrum of XLAS and may be useful for genetic counseling of this family. Further functional studies associated with genetic deficiency are warranted in the following research.

Noninvasive diagnosis of hereditary transthyretin-related cardiac amyloidosis: A case report

RATIONALE

Cardiac transthyretin amyloidosis is a progressive and fatal cardiomyopathy for which several promising therapies are in development. The diagnosis is frequently delayed or missed because of the limited specificity of clinical manifestations, routine electrocardiogram, echocardiography and the traditional requirement for endomyocardial biopsy confirmation.

PATIENT CONCERNS

A 68-year-old female had suffered from lumbago for 5 years with progressive weakness, numbness in both lower limb.

DIAGNOSIS

The patient's clinical signs were not specific, but cardiac amyloidosis was suspected based on relative left ventricular apical sparing of longitudinal strain on echocardiography and continuous elevated serum levels of cardiac biomarkers (ultrasensitive cardiac troponin I and NT-proBNP). She was finally diagnosed hereditary transthyretin-related cardiac amylodosis by specific findings of cardiovascular magnetic resonance imaging (CMR), -technetium pyrophosphate (Tc-PYP) scintigraphy and genetic testing.

INTERVENTIONS

The patient received medications including diuretics, beta-blockers and angiotensin-converting enzyme inhibitors at the time of hospitalization. Ultimately, however, she refused further treatments and requested discharge from our hospital.

OUTCOMES

A series of noninvasive technique enables the diagnosis of hereditary transthyretin-related cardiac amyloidosis.

LESSONS

While endomyocardial biopsy is not able to performed, this case demonstrates that a combination of noninvasive techniques, especially CMR, nuclear imaging, and genetic testing, may help us to make a correct diagnosis of hereditary transthyretin-related cardiac amyloidosis.

The identification of a transthyretin variant p.D38G in a Chinese family with early-onset leptomeningeal amyloidosis

Familial amyloid polyneuropathies (FAPs) are life-threatening, autosomal dominant diseases resulting, in most instances, from transthyretin gene (TTR) variants. A small number of TTR variants lead to leptomeningeal amyloidosis (LA), which is a rare FAP subtype with late-onset central nervous system (CNS) impairment symptoms. Previous studies suggest that LA's CNS selectivity was due to complete endoplasmic reticulum-associated degradation of highly destabilized mutants in peripheral tissues. LA's later age at onset (AAO) was due to lower choroid plexus secretory efficacy. This study reports on a family with LA, including six symptomatic and three presymptomatic members. The LA diagnosis was confirmed by leptomeningeal enhancement on contrast MRI, elevated cerebrospinal fluid protein levels, and positive Congo red staining. The predominant symptoms included headaches, dizziness, vomiting, hallucinations, and cognitive impairments which associated with obstructive hydrocephalus. The TTR p.D38G variant with the lowest secretory efficacy was identified as the genetic cause by whole exome sequencing. The family had a statistically significantly earlier mean AAO of 31.3 ± 7.4 (p = 0.001). These uncommon phenotypes indicate unknown factors influencing the progress of CNS impairment via TTR mutants. Medical imaging examinations suggest the potential early diagnosis value of contrast MRI and the importance of ependyma involvement in LA. LA genetic and clinical data were reviewed and summarized. These findings expand the FAPs' phenotypic spectrum and are valuable in FAP diagnosis, treatment, and further research.

Fluorotryptophan Incorporation Modulates the Structure and Stability of Transthyretin in a Site-Specific Manner

Abnormal deposition of aggregated wild-type (WT) human transthyretin (TTR) and its pathogenic variants is responsible for cardiomyopathy and neuropathy related to TTR amyloidosis. The tryptophan (Trp) fluorescence measurements typically used to study structural changes of TTR do not yield site-specific information on the two Trp residues per TTR protomer. To obtain such information, tryptophan labeled with fluorine at the 5 and 6 positions (5FW and 6FW) was incorporated into TTR. Fluorescence of 5FW and 6FW-labeled WT-TTR (WT-5FW and WT-6FW) and a single-Trp mutant W41Y showed that the photophysics of incorporated fluoro-Trp is consistent with site-specific solvation of the indole ring of W41 and W79. ¹⁹F-NMR showed that solvent accessibility depends on both the location of the Trp and the position of the fluorine substituent in the indole ring. Unexpectedly, differences were observed in the rates of aggregation, with WT-6FW aggregating more rapidly than WT-5FW or WT-TTR. Real-time ¹⁹F-NMR urea unfolding experiments revealed that WT-5FW is kinetically more stable than WT-6FW, consistent with the aggregation assay. In addition, structural perturbations of residues distant from either Trp site are more extensive in WT-6FW. Notably, residues in the dimer interfaces are perturbed by 6FW at residue 79; pathogenic mutations in these regions are associated with reduced tetramer stability and amyloidogenesis. The differences in behavior that arise from the replacement of a fluorine at the 5-position of a tryptophan with one at the adjacent 6-position emphasize the delicate balance of stability in the TTR tetramer.