Hyperferritinaemia-cataract syndrome: worldwide mutations and phenotype of an increasingly diagnosed genetic disorder

Four mutations identified in Chinese families with autosomal dominant congenital cataracts by next-generation sequencing

BACKGROUND

Congenital cataracts, which can arise due to a combination of factors like environmental influences and genetic predisposition, significantly impact children's visual health globally. The occurrence rate of congenital cataracts varies from 0. 63 to 9.74 per 10,000 births. There are 7.4 instances per 10,000 children, with the highest occurrence seen in Asia. Symptoms of the disease include clouding of the lens and visual impairment. Timely identification of the condition plays a crucial role in the management and outlook of pediatric patients.

OBJECTIVE

This investigation aimed to discover causative mutations in four separate Chinese family lineages.

METHODS

The detailed clinical data and family history of four Chinese families with autosomal dominant congenital cataracts were carefully documented. Examination of the Whole Exome Sequencing was utilized to identify the genetic anomalies present in the familial cases. Subsequent validation of the identified mutations was carried out using PCR and Sanger sequencing. Following this, various computational predictive programs were utilized to evaluate how the mutations impact the structure and function of the protein.

RESULTS

The sequencing results reveal four potential disease-causing mutations: c.436G > A (p.V146M) of CRYBB2 Family 1, c.26G > T (p.R9I) of GJA3 in family 2, c.227G > A (p.R76H) of GJA8 in family 3, c.-168G > T of FTL in family 4. Among them, the causative mutation in Family GJA3 is novel, and Family FTL is a rare cataract syndrome. These familial mutations showed complete co-segregation with the affected individuals, with no presence in unaffected family members or the 100 controls. Several bioinformatic prediction tools also support the likely pathogenicity of these mutations.

CONCLUSION

Our findings expand the mutational and phenotypic spectrum of genes associated with congenital cataracts and provide clues to the pathogenesis of congenital cataracts. These data also demonstrate the importance of NGS technology for the molecular diagnosis of congenital cataract patients.

Brazilian family with hyperferritinemia-cataract syndrome: case report

Hereditary hyperferritinemia-cataract syndrome is a rare autosomal dominant disease caused by a genetic mutation in the iron responsive element in the 5' untranslated region of the ferritin light chain gene. Hereditary hyperferritinemia-cataract syndrome is characterized by elevated serum ferritin levels and bilateral cataract development early in life and may be misdiagnosed as hemochromatosis. This case report describes a Brazilian family with a clinical diagnosis of hereditary hyperferritinemia-cataract syndrome, which was submitted to ferritin light chain gene sequencing. The genetic mutation c.-164C>G was identified in the 5' untranslated region. In conclusion, genetic testing can be used for accurate diagnosis of hereditary hyperferritinemia-cataract syndrome to avoid misdiagnosis of hemochromatosis, other diseases associated with iron overload or ophthalmic diseases.

Genetic Diagnosis in Hereditary Hemochromatosis: Discovering and Understanding the Biological Relevance of Variants

BACKGROUND

Hereditary hemochromatosis (HH) is a genetic disease, leading to iron accumulation and possible organ damage. Patients are usually homozygous for p. Cys282Tyr in the homeostatic iron regulator gene but may have mutations in other genes involved in the regulation of iron. Next-generation sequencing is increasingly being utilized for the diagnosis of patients, leading to the discovery of novel genetic variants. The clinical significance of these variants is often unknown.

CONTENT

Determining the pathogenicity of such variants of unknown significance is important for diagnostics and genetic counseling. Predictions can be made using in silico computational tools and population data, but additional evidence is required for a conclusive pathogenicity classification. Genetic disease models, such as in vitro models using cellular overexpression, induced pluripotent stem cells or organoids, and in vivo models using mice or zebrafish all have their own challenges and opportunities when used to model HH and other iron disorders. Recent developments in gene-editing technologies are transforming the field of genetic disease modeling.

SUMMARY

In summary, this review addresses methods and developments regarding the discovery and classification of genetic variants, from in silico tools to in vitro and in vivo models, and presents them in the context of HH. It also explores recent gene-editing developments and how they can be applied to the discussed models of genetic disease.

Conservation in the Iron Responsive Element Family

Iron responsive elements (IREs) are mRNA stem-loop targets for translational control by the two iron regulatory proteins IRP1 and IRP2. They are found in the untranslated regions (UTRs) of genes that code for proteins involved in iron metabolism. There are ten “classic” IRE types that define the conserved secondary and tertiary structure elements necessary for proper IRP binding, and there are 83 published “IRE-like” sequences, most of which depart from the established IRE model. Here are structurally-guided discussions regarding the essential features of an IRE and what is important for IRE family membership.

Hereditary hyperferritinemia-cataract syndrome in three Czech families: molecular genetic testing and clinical implications

BACKGROUND

Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal dominant disorder manifesting with high serum ferritin levels and the formation of early-onset cataracts, with numerous small opacities, predominantly in the lens cortex. HHCS is caused by mutations in the iron-responsive element of the FTL gene. The aim of this study was to establish a molecular diagnosis in three Czech probands with suspected HHCS.

METHODS

A complex ocular and systemic evaluation, including ferritin and iron measurements, was performed. The 5' untranslated region of FTL was directly sequenced in all available family members, followed by paternity testing in one family.

RESULTS

Three different FLT pathogenic variants (c.-161C>T, c.-167C>T, and c.-168G>C) present in the heterozygous state were detected in each of the 3 probands. Two segregated with the disease phenotype within the families, but c.-167C>T occurred de novo (confirmed by paternity testing). Prior to establishing molecular diagnosis, two probands were misdiagnosed with hemochromatosis. One individual, aged 43 years, underwent phlebotomy; another, aged 8.5 years, was treated with the iron chelator deferasirox, leading to life-threatening acute hyperammonemia, without severe liver injury.

CONCLUSIONS

Lack of family history does not exclude HHCS, because the pathogenic variant can arise de novo. Noncoding regions are often omitted from diagnostic gene panels, thus evading detection. Careful clinical evaluations and targeted genetic screening are important for avoiding potentially harmful treatments.

Hereditary hyperferritinaemia-cataract syndrome (HHCS) – an underestimated condition: ferritin light chain variant spectrum in German families

Background

In hereditary hyperferritinaemia-cataract syndrome (HHCS), single nucleic acid alterations in the ferritin light chain (L-ferritin) iron response element (IRE) constitutively derepress ferritin synthesis, resulting in hyperferritinaemia, L-ferritin deposits in the lens of the eye and early bilateral cataract onset.

Methods

In this study, six German families with putative HHCS were analysed. Clinical diagnosis of HHCS was based on medical history, evaluation of ferritin serum levels, transferrin saturation and clinical ophthalmological examination. Diagnosis was confirmed by polymerase chain reaction (PCR)-based DNA sequencing of the L-ferritin IRE.

Results

Genetic analysis of the L-ferritin IRE revealed relevant single nucleic acid alterations in each of the affected families. Variants c.-168G > A, c.-168G > U and c.-167C > U were located in the C-bulge region; and variants c.-161C > U and c.-157G > A were located in the hexanucleotide loop of the L-ferritin IRE.

Conclusions

Family history of hyperferritinaemia and juvenile cataracts are strong indicators of HHCS. Genetic analysis of the L-ferritin IRE is a straightforward procedure to confirm the diagnosis. Accurate diagnosis of hyperferritinaemia can avoid unnecessary treatment by venesection, and focus attention on early cataract detection in offspring at risk.

Elevated serum ferritin level with cataract of spectacular morphology: Hyperferritinemia-cataract syndrome

Hyperferritinemia-cataract syndrome, characterized by high serum ferritin concentration and cataracts in early life, remains a less-known rare disease, with fewer than 100 families reported worldwide. Though benign, high ferritin levels frequently result in misdiagnosis with iron storage disease, and patients can be exposed to unnecessary, even invasive, evaluation and treatment procedures. The presence of cataract together with isolated serum ferritin elevation should alert clinicians to consider this syndrome. We herein present a new family with hyperferritinemia-cataract syndrome to increase clinical awareness.

Repression of ferritin light chain translation by human eIF3

A central problem in human biology remains the discovery of causal molecular links between mutations identified in genome-wide association studies (GWAS) and their corresponding disease traits. This challenge is magnified for variants residing in non-coding regions of the genome. Single-nucleotide polymorphisms (SNPs) in the 5ʹ untranslated region (5ʹ-UTR) of the ferritin light chain (FTL) gene that cause hyperferritinemia are reported to disrupt translation repression by altering iron regulatory protein (IRP) interactions with the FTL mRNA 5ʹ-UTR. Here, we show that human eukaryotic translation initiation factor 3 (eIF3) acts as a distinct repressor of FTL mRNA translation, and eIF3-mediated FTL repression is disrupted by a subset of SNPs in FTL that cause hyperferritinemia. These results identify a direct role for eIF3-mediated translational control in a specific human disease.

A novel double nucleotide variant in the ferritin-L iron-responsive element in a Finnish patient with hereditary hyperferritinaemia-cataract syndrome

PURPOSE

To present a novel Finnish double nucleotide variant in the iron-responsive element (IRE) of the ferritin L-chain gene (FTL) leading to hyperferritinaemia-cataract syndrome (HHCS).

METHODS

Genomic DNA extracted from peripheral blood leucocytes and synthetized with three different primers flanking the IRE in the FTL 5'-untranslated region of the FTL was used in polymerase chain reaction (PCR). Thereafter, Sanger sequencing was performed on the 487-bp and 602-bp PCR amplification products with specific primers to reveal FTL IRE mutations.

RESULTS

A 58-year-old female patient with elevated serum ferritin level (1339 μg/l) was diagnosed with HHCS after extensive workup. Genetic testing identified a novel double point mutation g.48965355G>C (chr19, hg19) and g.48965356G>T (chr19, hg19) in the lower stem region of the IRE canonical structure of the FTL.

CONCLUSION

After excluding other causes, elevated serum ferritin level in a person with early onset cataract is indicative for HHCS, a genetic disorder caused by mutation in the IRE of the FTL.

Ferritin light chain gene mutations in two Brazilian families with hereditary hyperferritinemia-cataract syndrome

Hereditary hyperferritinemia-cataract syndrome is an autosomal dominant genetic disorder associated with mutations in the 5’UTR region of the ferritin light chain gene. These mutations cause the ferritin levels to increase even in the absence of iron overload. Patients also develop bilateral cataract early due to accumulation of ferritin in the lens, and many are misdiagnosed as having hemochromatosis and thus not properly treated. The first cases were described in 1995 and several mutations have already been identified. However, this syndrome is still a poorly understood. We report two cases of unrelated Brazilian families with clinical suspicion of the syndrome, which were treated in our department. For the definitive diagnosis, the affected patients, their parents and siblings were submitted to Sanger sequencing of the 5’UTR region for detection of the ferritin light gene mutation. Single nucleotide polymorphism-like mutations were found in the affected patients, previously described. The test assisted in making the accurate diagnosis of the disease, and its description is important so that the test can be incorporated into clinical practice.

RPFdb: a database for genome wide information of translated mRNA generated from ribosome profiling

Translational control is crucial in the regulation of gene expression and deregulation of translation is associated with a wide range of cancers and human diseases. Ribosome profiling is a technique that provides genome wide information of mRNA in translation based on deep sequencing of ribosome protected mRNA fragments (RPF). RPFdb is a comprehensive resource for hosting, analyzing and visualizing RPF data, available at www.rpfdb.org or http://sysbio.sysu.edu.cn/rpfdb/index.html. The current version of database contains 777 samples from 82 studies in 8 species, processed and reanalyzed by a unified pipeline. There are two ways to query the database: by keywords of studies or by genes. The outputs are presented in three levels. (i) Study level: including meta information of studies and reprocessed data for gene expression of translated mRNAs; (ii) Sample level: including global perspective of translated mRNA and a list of the most translated mRNA of each sample from a study; (iii) Gene level: including normalized sequence counts of translated mRNA on different genomic location of a gene from multiple samples and studies. To explore rich information provided by RPF, RPFdb also provides a genome browser to query and visualize context-specific translated mRNA. Overall our database provides a simple way to search, analyze, compare, visualize and download RPF data sets.

Hereditary hyperferritinemia cataract syndrome as a cause of childhood hyperferritinemia

A 2-year-old female was presented with high levels of serum ferritin (890 ng/mL) in a routine blood test. Clinical and laboratory investigations excluded the presence of iron overload and secondary causes of hyperferritinemia. A detailed family history and laboratory examinations revealed the presence of early-onset cataract in her 33-year-old mother, who also displayed hyperferritinemia (633 ng/mL), similar to other family members. Genetic testing confirmed the diagnosis of hereditary hyperferritinemia cataract syndrome (HHCS), demonstrating a C39>G (c.-161C>G) mutation into FTL gene. HHCS should be considered in the differential diagnosis of childhood hyperferritinemia, especially in the presence of normal transferrin saturation.

A novel deletion in the iron-response element of the L-ferritin gene, causing hyperferritinaemia cataract syndrome

A 47-year-old woman, presenting to her family physician with fatigue, was incidentally found to have persistently elevated ferritin. There was clinically no suggestion of iron overload, and laboratory testing showed transferrin saturation at the low end of the reference range. After ruling out acquired causes of hyperferritinaemia, as well as laboratory interference, further questioning revealed a history of bilateral early-onset cataracts, allowing a diagnosis of hyperferritinaemia cataract syndrome to be made. DNA sequencing of the 5' untranslated region of the L-ferritin gene revealed a novel 4-base deletion in the iron response element, within a region known to be crucial for binding iron regulatory protein.

Raised serum ferritin concentration in hereditary hyperferritinemia cataract syndrome is not a marker for iron overload

Hyperferritinemia and bilateral cataracts are features of the rare hereditary hyperferritinemia cataract syndrome (HHCS; OMIM #600886). HHCS is an autosomal dominant condition caused by mutations which increase expression of the ferritin light polypeptide (FTL) gene. We report a patient with HHCS who was misdiagnosed and treated as having hemochromatosis, in whom a heterozygous c.-160A>G mutation was identified in the iron responsive element (IRE) of FTL, causing ferritin synthesis in the absence of iron overload. This report demonstrates the need for clinical awareness of HHCS as a cause of hyperferritinemia in the absence of iron overload and provides a possible diagnostic schema.

Newborn mouse lens proteome and its alteration by lysine 6 mutant ubiquitin

Ubiquitin is a tag that often initiates degradation of proteins by the proteasome in the ubiquitin proteasome system. Targeted expression of K6W mutant ubiquitin (K6W-Ub) in the lens results in defects in lens development and cataract formation, suggesting critical functions for ubiquitin in lens. To study the developmental processes that require intact ubiquitin, we executed the most extensive characterization of the lens proteome to date. We quantified lens protein expression changes in multiple replicate pools of P1 wild-type and K6W-Ub-expressing mouse lenses. Lens proteins were digested with trypsin, peptides were separated using strong cation exchange and reversed-phase liquid chromatography, and tandem mass (MS/MS) spectra were collected with a linear ion trap. Transgenic mice that expressed low levels of K6W-Ub (low expressers) had normal, clear lenses at birth, whereas the lenses that expressed high levels of K6W-Ub (higher expressers) had abnormal lenses and cataracts at birth. A total of 2052 proteins were identified, of which 996 were reliably quantified and compared between wild-type and K6W-Ub transgenic mice. Consistent with a delayed developmental program, fiber-cell-specific proteins, such as γ-crystallins (γA, γB, γC, and γE), were down-regulated in K6W-Ub higher expressers. Up-regulated proteins were involved in energy metabolism, signal transduction, and proteolysis. The K6W-Ub low expressers exhibited delayed onset and milder cataract consistent with smaller changes in protein expression. Because lens protein expression changes occurred prior to lens morphological abnormalities and cataract formation in K6W-Ub low expressers, it appears that expression of K6W-Ub sets in motion a process of altered protein expression that results in developmental defects and cataract.

Human L-ferritin deficiency is characterized by idiopathic generalized seizures and atypical restless leg syndrome

Human L-ferritin deficiency causes reduced cellular iron availability and increased ROS production with enhanced oxidized proteins, which results in idiopathic generalized seizures and atypical restless leg syndrome.

The ubiquitously expressed iron storage protein ferritin plays a central role in maintaining cellular iron homeostasis. Cytosolic ferritins are composed of heavy (H) and light (L) subunits that co-assemble into a hollow spherical shell with an internal cavity where iron is stored. The ferroxidase activity of the ferritin H chain is critical to store iron in its Fe3+ oxidation state, while the L chain shows iron nucleation properties. We describe a unique case of a 23-yr-old female patient affected by a homozygous loss of function mutation in the L-ferritin gene, idiopathic generalized seizures, and atypical restless leg syndrome (RLS). We show that L chain ferritin is undetectable in primary fibroblasts from the patient, and thus ferritin consists only of H chains. Increased iron incorporation into the FtH homopolymer leads to reduced cellular iron availability, diminished levels of cytosolic catalase, SOD1 protein levels, enhanced ROS production and higher levels of oxidized proteins. Importantly, key phenotypic features observed in fibroblasts are also mirrored in reprogrammed neurons from the patient’s fibroblasts. Our results demonstrate for the first time the pathophysiological consequences of L-ferritin deficiency in a human and help to define the concept for a new disease entity hallmarked by idiopathic generalized seizure and atypical RLS.

Novel mutations in the ferritin-L iron-responsive element that only mildly impair IRP binding cause hereditary hyperferritinaemia cataract syndrome

Background

Hereditary Hyperferritinaemia Cataract Syndrome (HHCS) is a rare autosomal dominant disease characterized by increased serum ferritin levels and early onset of bilateral cataract. The disease is caused by mutations in the Iron-Responsive Element (IRE) located in the 5^′ untranslated region of L-Ferritin (FTL) mRNA, which post-transcriptionally regulates ferritin expression.

Methods

We describe two families presenting high serum ferritin levels and juvenile cataract with novel mutations in the L-ferritin IRE. The mutations were further characterized by in vitro functional studies.

Results

We have identified two novel mutations in the IRE of L-Ferritin causing HHCS: the Badalona +36C > U and the Heidelberg +52 G > C mutation. Both mutations conferred reduced binding affinity on recombinant Iron Regulatory Proteins (IPRs) in EMSA experiments. Interestingly, the Badalona +36C > U mutation was found not only in heterozygosity, as expected for an autosomal dominant disease, but also in the homozygous state in some affected subjects. Additionally we report an update of all mutations identified so far to cause HHCS.

Conclusions

The Badalona +36C > U and Heidelberg +52 G > C mutations within the L-ferritin IRE only mildly alter the binding capacity of the Iron Regulatory Proteins but are still causative for the disease.

Congenital Hyperferritinemia Diagnosed in A 2 Month Old-A Case Report from India

BACKGROUND

In clinical medicine, ferritin is predominantly utilized as a serum marker of total body iron stores. In cases of iron deficiency and overload, serum ferritin serves a critical role in both diagnosis and management. Elevated serum and tissue ferritin are linked to coronary artery disease, malignancy, and poor outcomes following stem cell transplantation. Ferritin is directly implicated in less common but potentially devastating human diseases including sideroblastic anemias, neurodegenerative disorders, and hemophagocytic syndrome.

METHOD

We report a case of congenital hyperferritinemia with serum iron within reference range, along with bronchopneumonia, acyanotic congenital heart disease, anemia, hypocalcaemia and dysmorphism in a 2 month old baby. Symptomatic treatment was given.

RESULT

The baby was discharged after 7 days. In a stable condition and having gained some weight.He was diagnosed as a case of congenital hyperferritinemia as C reactive protein levels normalized but ferritin levels remained high and A37C mutation within the iron-responsive element of L-ferritin was detected. He was born to consanguineous parents, there was history of cataract in the family and his mother also had high serum ferritin levels.

CONCLUSION

This case is an example of the detection of a rare genetic disorder in a child admitted with apparently innocuous symptoms of fever and inflammation. Our case underlines the importance of monitoring ferritin levels, along with other signs of inflammation in order to differentiate congenital hyperferritinemia from inflammatory cause.

A child with hyperferritinemia: case report

Hereditary hyperferritinemia cataract syndrome (HHCS) is a rare condition caused by mutations in the gene coding for the light chain of ferritin; it does not lead to iron overload, but it is associated with the risk of developing a bilateral nuclear cataract also in childhood. On the contrary, a raise of serum ferritin levels is a common finding in pediatrics. We describe here a case of HHCS that offers some interesting clues for the daily practice. Our patient is a 6 year old Italian boy who came to our attention after some time of diagnostic uncertainties because of persistently high levels of ferritin with no apparent cause. We were guided to the suspect of this syndrome by the family history (5 members with various degrees of cataract developed in first infancy). High levels of serum ferritin and specific genetic testing (mutation A37C) confirmed the diagnosis. This case underlines the need of considering rare genetic syndromes, including hereditary hyperferritinemia cataract syndrome, in the differential diagnosis of raised serum ferritin in children and the importance of paying attention to family history in considering a patient with isolated raised levels of serum ferritin.