Characterisation of ACP5 missense mutations encoding tartrate-resistant acid phosphatase associated with spondyloenchondrodysplasia

Detection of genetic mutations underlying early-onset systemic lupus erythematosus

OBJECTIVE

We aimed to investigate the presence of monogenic causes of systemic lupus erythematosus (SLE) in our early-onset SLE patients.

METHODS

Fifteen pediatric SLE cases who had early disease onset (≤6 years) were enrolled in this study. All patients fulfilled the Systemic Lupus International Collaborating Clinics (SLICC) criteria. Genomic DNA was used for whole exome sequencing (WES). Pathogenic variants were confirmed by Sanger sequencing.

RESULTS

The median age at diagnosis of 15 early-onset SLE patients included in the study was 4 (2-6) years (F/M = 12/3). Significant gene mutations were detected in five of these patients (33.3%). Patients 1 and 2 with homozygous DNASE1L3 mutations [c.320+4_320+7del and G188 A (c.563 G>C) variants] had skin involvement and oral ulcers. One of them (patient 1) had arthritis and nephritis, and another (patient 2) had nonscarring alopecia and thrombocytopenia. They are currently clinically inactive but have positive serological findings. Patient 3 with homozygous pathogenic ACP5 mutation [G109 R (c.325 G>A) variant] had arthritis, nephritis, short stature, and skeletal dysplasia. Patient 4 with a heterozygote novel IFIH1 mutation [L809 F (c.2425 C>T) variant] had skin findings and leukopenia. Patient 5 with novel C1S variant [homozygous C147 W (c.441 C>G) variant] had marked skin findings, oral ulcers, nonscarring alopecia, pancytopenia, and low total hemolytic complement CH50 level. All patients have responded to the treatments and have low Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores, on therapy.

CONCLUSION

Genetic causes should be investigated in early-onset SLE, for better management and genetic counseling. On the other hand, multicenter studies may help to further define genotype-phenotype associations.

Autoimmune Hemolytic Anemia Due to Spondyloenchondrodysplasia with Spastic Paraparesis and Intracranial Calcification due to Mutation in ACP5

Spondyloenchondrodysplasia (SPENCD) is a rare spondylometaphyseal skeletal dysplasia with characteristic lesions mimicking enchondromatosis and resulting in short stature. A large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders. SPENCD is caused by loss of tartrate-resistant acid phosphatase activity, due to homozygous mutations in ACP5 , playing a role in nonnucleic-acid-related stimulation/regulation of the type I interferon pathway. In this article, we presented a 19-year-old boy with SPENCD, presenting with recurrent autoimmune hemolytic anemia episodes since he was 5 years old. He had short stature, platyspondyly, metaphyseal changes, intracranial calcification, spastic paraparesis, and mild intellectual disability. He also had recurrent pneumonia attacks. The clinical diagnosis of SPENCD was confirmed by sequencing of the ACP5 gene, and a homozygous c.155A > C (p.K52T) variation was found, which was reported before as pathogenic. In conclusion, in early onset chronic autoimmune cytopenias an immune dysregulation may often have a role in the etiology. Associating findings and immunologic functions should be carefully evaluated in such patients in the light of the literature. The present case shows the importance of multisystemic evaluation for the detection of SPENCD that has a monogenic etiology.

Biomimetics for purple acid phosphatases: A historical perspective

Biomimetics hold potential for varied applications in biotechnology and medicine but have also attracted particular interest as benchmarks for the functional study of their more complex biological counterparts, e.g. metalloenzymes. While many of the synthetic systems adequately mimic some structural and functional aspects of their biological counterparts the catalytic efficiencies displayed are mostly far inferior due to the smaller size and the associated lower complexity. Nonetheless they play an important role in bioinorganic chemistry. Numerous examples of biologically inspired and informed artificial catalysts have been reported, designed to mimic a plethora of chemical transformations, and relevant examples are highlighted in reviews and scientific reports. Herein, we discuss biomimetics of the metallohydrolase purple acid phosphatase (PAP), examples of which have been used to showcase synergistic research advances for both the biological and synthetic systems. In particular, we focus on the seminal contribution of our colleague Prof. Ademir Neves, and his group, pioneers in the design and optimization of suitable ligands that mimic the active site of PAP.

Genetic Parameter Estimation and Whole Sequencing Analysis of the Genetic Architecture of Chicken Keel Bending

Bone health is particularly important for high-yielding commercial layer chickens. The keel of poultry is an extension of the abdomen side of the sternum along the sagittal plane and is one of the most important bones. In this study, the keel phenotype of White Leghorns laying hen flocks showed significant individual differences. To clarify its genetic mechanism, we first estimated the heritability of keel bend (KB) in White Leghorn, recorded the production performance of the chicken flock, examined the blood biochemical indexes and bone quality in KB and keel normal (KN) chickens, and performed whole-genome pooled sequencing in KB and KN chickens. We then performed selection elimination analysis to determine the genomic regions that may affect the keel phenotypes. The results show that KB is a medium heritability trait. We found that cage height had a significant effect on the KB (p < 0.01). At 48 weeks, there were significant differences in the number of eggs, the number of normal eggs, and eggshell strength (p < 0.05). The content of parathyroid hormone was lower (p < 0.01) and that of calcitonin was higher (p < 0.01) in KB chickens than in KN chickens. The differences in bone mineral density, bone strength, and bone cortical thickness of the humerus and femur were extremely significant (p < 0.01), with all being lower in KB chickens than in KN chickens. In addition, the bones of KB chickens contained more fat organization. A total of 128 genes were identified in selective sweep regions. We identified 10 important candidate genes: ACP5, WNT1, NFIX, CNN1, CALR, FKBP11, TRAPPC5, MAP2K7, RELA, and ENSGALG00000047166. Among the significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways found, we identifed two bone-related pathways, one involving “osteoclast differentiation” and the other the “MAPK signaling pathway.” These results may help us better understand the molecular mechanism of bone traits in chickens and other birds and provide new insights for the genetic breeding of chickens.

Monogenic lupus due to spondyloenchondrodysplasia with spastic paraparesis and intracranial calcification: case-based review

Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia characterized with platyspondyly and metaphyseal lesions of the long bones mimicking enchondromatosis, resulting in short stature. SPENCD often coexists with neurologic disorders and immune dysregulation. Spasticity, developmental delay and intracranial calcification are main neurologic abnormalities. Large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders with autoimmune thrombocytopenia and systemic lupus erythematosus as the most common phenotypes. SPENCD is caused by loss of tartrate-resistant acid phosphatase (TRAP) activity, due to homozygous mutations in ACP5, playing a role in non-nucleic acid-related stimulation/regulation of the type I interferon pathway. We present two siblings, 13-year-old girl and 25-year-old boy with SPENCD, from consanguineous parents. Both patients had short stature, platyspondyly, metaphyseal changes, spastic paraparesis, mild intellectual disability, and juvenile-onset SLE. The age at disease-onset was 2 years for girl and 19 years for boy. Both had skin and mucosa involvement. The age at diagnosis of SLE was 4 years for girl, and 19 years for boy. The clinical diagnosis of SPENCD was confirmed by sequencing of ACP5 gene, which revealed a homozygous c.155A > C (p.K52T), a variant reported before as pathogenic. Juvenile-onset SLE accounts for about 15-20% of all SLE cases. But, the onset of SLE before 5-years of age and also monogenic SLE are rare. Our case report and the literature review show the importance of multisystemic evaluation in the diagnosis of SPENCD and to remind the necessity of investigating the monogenic etiology in early-onset and familial SLE cases.

Monogenic lupus due to spondyloenchondrodysplasia with spastic paraparesis and intracranial calcification: case-based review

Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia characterized with platyspondyly and metaphyseal lesions of the long bones mimicking enchondromatosis, resulting in short stature. SPENCD often coexists with neurologic disorders and immune dysregulation. Spasticity, developmental delay and intracranial calcification are main neurologic abnormalities. Large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders with autoimmune thrombocytopenia and systemic lupus erythematosus as the most common phenotypes. SPENCD is caused by loss of tartrate-resistant acid phosphatase (TRAP) activity, due to homozygous mutations in ACP5, playing a role in non-nucleic acid-related stimulation/regulation of the type I interferon pathway. We present two siblings, 13-year-old girl and 25-year-old boy with SPENCD, from consanguineous parents. Both patients had short stature, platyspondyly, metaphyseal changes, spastic paraparesis, mild intellectual disability, and juvenile-onset SLE. The age at disease-onset was 2 years for girl and 19 years for boy. Both had skin and mucosa involvement. The age at diagnosis of SLE was 4 years for girl, and 19 years for boy. The clinical diagnosis of SPENCD was confirmed by sequencing of ACP5 gene, which revealed a homozygous c.155A > C (p.K52T), a variant reported before as pathogenic. Juvenile-onset SLE accounts for about 15–20% of all SLE cases. But, the onset of SLE before 5-years of age and also monogenic SLE are rare. Our case report and the literature review show the importance of multisystemic evaluation in the diagnosis of SPENCD and to remind the necessity of investigating the monogenic etiology in early-onset and familial SLE cases.