Sanger sequencing in exonic regions of STK11 gene uncovers a novel de-novo germline mutation (c.962_963delCC) associated with Peutz-Jeghers syndrome and elevated cancer risk: case report of a Chinese patient

New Insights Into the Complex Mutational Landscape of Sézary Syndrome

Sézary syndrome (SS) is a genetically and clinically distinct entity among cutaneous T-cell lymphomas (CTCL). SS is characterized by more aggressive disease compared to the most common indolent type of CTCL, mycosis fungoides. However, there are limited available genomic data regarding SS. To characterize and expand current mappings of the genomic landscape of CTCL, whole exome sequencing (WES) was performed on peripheral blood samples from seven patients with SS. We detected 21,784 variants, of which 21,140 were novel and 644 were previously described. Filtering revealed 551 nonsynonymous variants among 525 mutated genes−25 recurrent mutations and 1 recurrent variant. Several recurrently mutated genes crucial to pathogenesis pathways, including Janus kinase (JAK)/signal transducers and activators of transcription (STAT), peroxisome proliferator-activated receptors (PPAR), PI3K-serine/threonine protein kinases (AKT), and fibroblast growth factor receptors (FGFR), were identified. Furthermore, genetic mutations spanned both known and novel genes, supporting the idea of a long-tail distribution of mutations in lymphoma. Acknowledging these genetic variants and their affected pathways may inspire future targeted therapies. WES of a limited number of SS patients revealed both novel findings and corroborated complexities of the “long-tail” distribution of previously reported mutations.

Molecular epidemiology, pathogenicity, and structural analysis of haemoglobin variants in the Yunnan province population of Southwestern China

Abnormal haemoglobin (Hb) variants result in the most commonly inherited disorders in humans worldwide. In this study, we investigated the molecular epidemiology characteristics of Hb variants, along with associated structural and functional predictions in the Yunnan province population of Southwestern China. A total of 41,933 subjects who sought haemoglobinopathy screening were included. Based on bioinformatics and structural analysis, as well as protein modeling, the pathogenesis and type of Hb genetic mutations were characterized. Among all individuals studied, 328 cases (0.78%) were confirmed as carriers of Hb variants, with 13 cases (0.03%) presenting α-globin variants, 313 (0.75%) β-globin variants, and two δ-globin variants. A total of 19 different mutations were identified, including three novel mutations. In addition, 48 cases of αα^CS mutations and 14 cases of Hb H or Hb Bart’s were found. The isoelectric point, evolutionary conservation, and genotype-phenotype correlation for these mutations were predicted. Additionally, secondary and tertiary protein structure modeling were performed for three selected mutations. In conclusion, the prevalence of Hb variants in the Yunnan population is much higher than other regions of China. Complete characterization of these Hb variants is essential for generating a rational strategy to control the haemoglobinopathies in this region.

Early screening the small bowel is key to protect Peutz-Jeghers syndrome patients from surgery: a novel mutation c.243delG in STK11 gene

Background

Peutz-Jeghers syndrome (PJS) is a Mendelian disease, whose causative gene is STK11, mainly characterized by gastrointestinal polyposis and increased cancer risk. Clinical observation reveals intussusception in childhood are more frequent and severe than in adults, and it is difficult to prevent this knotty complication.

Case presentation

A boy without a positive family history grew oral MP after birth and developed abdominal pain and bloody stood at 7 years old. Endoscopy revealed multiple polyps within the colon and the ileum, and endoscopic polypectomy and regular surveillance protected him from severe complications and open surgeries. A heterozygous deletion in STK11, c.243delG, was detected in the proband but not in his parents. This mutation has not been documented in databases.

Conclusions

We suspect a child of PJS may need a more thorough endoscopic examination including enteroscopy or capsule endoscopy to take care of small bowel when PJS related symptoms comes up.

Analysis of deletional hereditary persistence of fetal hemoglobin/δβ-thalassemia and δ-globin gene mutations in Southerwestern China

Background

Deletional hereditary persistence of fetal hemoglobin (HPFH)/δβ‐thalassemia and δ‐thalassemia are rare inherited disorders which may complicate the diagnosis of β‐thalassemia. The aim of this study was to reveal the frequency of these two disorders in Southwestern China.

Methods

A total of 33,596 subjects were enrolled for deletional HPFH/δβ‐thalassemia, and positive individuals with high fetal hemoglobin (Hb F) level were diagnosed by multiplex ligation‐dependent probe amplification (MLPA). A total of 17,834 subjects were analyzed for mutations in the δ‐globin gene. Positive samples with low Hb A₂ levels were confirmed by δ‐globin gene sequencing. Furthermore, the pathogenicity and construction of a selected δ‐globin mutation were analyzed.

Results

A total of 92 suspected cases with Hb F ≥5.0% were further characterized by MLPA. Eight different deletional HPFH/δβ‐thalassemia were observed at a frequency of 0.024%. In addition, 195 cases suspected to have a δ‐globin gene mutation (Hb A₂ ≤2.0%) were characterized by molecular analysis. δ‐Globin gene mutation was found at a frequency of 0.49% in Yunnan. The pathogenicity and construction for a selected δ‐globin mutation was predicted.

Conclusion

Screening of these two disorders was analyzed in Southwestern China, which could define the molecular basis of these conditions in this population.

The altered activity of P53 signaling pathway by STK11 gene mutations and its cancer phenotype in Peutz-Jeghers syndrome

Background

Peutz-Jeghers syndrome (PJS) is caused by mutations in serine/threonine kinase 11 (STK11) gene. The increased cancer risk has been connected to P53 pathway.

Methods

PJS probands with STK11 mutation were included in the function analysis. P53 activity elevated by STK11 mutants was investigated using dual-luciferase reporter assay in vitro after constructing expression vectors of STK11 wild type and mutants generated by site-directed substitution. The association between the P53 activity and clinicopathological factors was analysis, especially the cancer history.

Results

Thirteen probands with STK11 mutations were involved, and within the mutations, c.G924A was novel. P53 activity elevation caused by 6 truncating mutations were significantly lower than that of STK11 wild type (P < 0.05). Family history of cancer was observed in 5 families. Within them, P53 activity was reduced and cancer occurred before 40 in 2 families, while it was not significantly changed and cancers happened after 45 in the other 3 families.

Conclusions

The affected P53 activity caused by STK11 mutations in PJS patients is significantly associated with protein truncation, while cancer risk in PJS can be elevated through pathways rather than P53 pathway. P53 activity test is probably a useful supporting method to predict cancer risk in PJS, which could be helpful in clinical practice.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0626-5) contains supplementary material, which is available to authorized users.

Close and regular surveillance is key to prevent severe complications for Peutz-Jeghers syndrome patients without gastrointestinal polyps: case report of a novel STK11 mutation (c.471_472delCT) in a Chinese girl

Background

Peutz-Jeghers syndrome (PJS) is a Mendelian disease characterized by gastrointestinal hamartomas, mucocutaneous pigmentation (MP), and increased cancer risk. Serine/threonine kinase 11 (STK11) is the only validated causative gene in PJS. Clinical observation reveals MP and intussusception in childhood are more frequent and severe than in adults.

Case presentation

We report here a girl without a positive family history, who grew oral and fingertip MP at her age of 2 and got abdomen dull pain from 7 years old. Endoscopy revealed no obvious polyps in the stomach or the colon until 10 years old, when she received enteroscopy. Tens of polyps were resected during enteroscopy, and pathological examination confirmed them hamartomas. A heterozygous deletion in STK11, c.471_472delCT, was detected in the proband but not in her parents, which is not recorded in databases.

Conclusion

The mutation we reported here is a novel one and a de-novo one, so our results enlarge the spectrum of STK11. We speculate close and regular endoscopy especially enteroscopy is necessary for complication prevention when the former endoscopy discovers no polyps temporarily in a child of suspect PJS.

A novel germline mutation (c.A527G) in STK11 gene causes Peutz-Jeghers syndrome in a Chinese girl: A case report

RATIONALE

Peutz-Jeghers syndrome (PJS) is a Mendelian autosomal dominant disease caused by mutations in the tumor suppressor gene, serine/threonine kinase 11 (STK11). The features of this syndrome include gastrointestinal (GI) hamartomas, melanin spots on the lips and the extremities, and an increased risk of developing cancer. Early onset of disease is often characterized by mucocutaneous pigmentation and intussusception due to GI polyps in childhood.

PATIENT CONCERNS

A girl with a positive family history grew oral pigmentation at 1 and got intussusception by small bowel hamartomas at 5.

DIAGNOSES

She was diagnosed with PJS based on oral pigmentation and a positive family history of PJS.

INTERVENTIONS

Enteroscopy was employed to treat the GI polyps. Sanger sequencing was used to investigate STK11 mutation in this family.

OUTCOMES

A large jejunal polyp together with other smaller ones was resected, and the girl recovered uneventfully. We discovered a heterozygous substitution in STK11, c.A527G in exon 4, in the girl and her father who was also a PJS patient, and the amine acid change was an aspartic acid-glycine substitution in codon 176. This mutation was not found in other healthy family members and 50 unrelated non-PJS controls, and it is not recorded in databases, which prove it a novel mutation. Evolutionary conservation analysis of amino acid residues showed this aspartic acid is a conserved one between species, and protein structure prediction by SWISS-MODEL indicated an obvious change in local structure. In addition, PolyPhen-2 score for this mutation is 1, which indicates it probably damaging.

LESSONS

PJS can cause severe complication like intussusception in young children, and early screening for small bowel may be beneficial for these patients. The mutation of STK11 found in this girl is a novel one, which enlarges the spectrum of STK11. Our analysis supported it a causative one in PJS.