Structural maintenance of chromosomes (SMC), including cohesin, condensin and the SMC5/6 complex, are protein complexes which maintain the higher structure and dynamic stability of chromatin. Such circular complexes, with similar structures, play pivotal roles in chromatid cohesion, chromosomal condensation, DNA replication and repair, as well as gene transcription. Despite extensive research on the functions of the SMCs, our understanding of the SMC5/6 complex has remained limited compared with the other two complexes. This article has reviewed the architecture and crucial physiological roles of the SMCs, and explored the associated phenotypes resulting from mutations of the SMC components such as Cornelia de Lange syndrome (CdLS) and microcephaly, with an aim to provide insights into their functions in eukaryotic cells and implications for human diseases.

Objective:To evaluate the outcomes of reconstruction with half of peroneous longus tendon autograft for the treatment of chronic Achilles tendon rupture combined with tendon defects.Methods:A retrospective case series study was conducted on the clinical data of 14 patients with chronic tendon rupture combined with defects admitted to Orthopedic Sports Medicine Center, West China Hospital, Sichuan University from November 2017 to August 2020, including 11 males and 3 females, aged 26-62 years [(42.8±10.7)years]. All the patients underwent Achilles tendon reconstruction with half of peroneus longus tendon autograft. American Orthopedic Foot and Ankle Society (AOFAS) score, Achilles tendon total rupture score (ATRS) and Visual Analogue Scale (VAS) were compared before surgery, at 12 months after surgery and at the last follow-up. At the last follow-up, MRI of the injured ankle was prescribed to evaluate tendon healing; Thomspon test was performed and the patients were asked to do single-leg heel raise; the patients were asked about their conditions in returning to daily life activities and sports. Postoperative complications were observed.Results:All the patients were followed up for 24-47 months [(35±9)months]. AOFAS score, ATRS and VAS at 12 months after surgery were (87.9±6.6)points, (80.9±2.4)points and (2.0±0.3)points respectively, superior to those before surgery [(52.7±16.9)points, (42.0±4.4)points and (4.1±0.4)points respectively] ( P<0.05). The afore-mentioned results at the last follow-up were (95.2±7.2)points, (85.9±2.5)points and (0.8±0.3)points respectively, superior to those at 12 months after surgery ( P<0.05). MRI images of the affected ankle joints showed satisfactory healing of the reconstructed Achilles tendon at the last follow-up. All the patients, being negative in Thompson test at the last follow-up, were able to complete the heel lift on the affected side. All the patients resumed activities of daily living at the last follow-up, among whom 5 resumed to moderate- to high-intensity sports activities, such as basketball sport, and moderate-to high-intensity physical training, 5 resumed light-intensity sports activities such as jogging and swimming, and the other 4 did not resume sports due to fear of re-injury or aging. One patient had delayed wound healing, which was considered gout-related. One patient complained about mild pain at the Achilles tendon in cold weather or after long walks. No re-rupture of the Achilles tendon occurred. No patient complained about discomfort at the graft harvest site, calcaneal valgus or restricted ankle plantar flexion. Conclusions:For patients with chronic Achilles tendon rupture combined with tendon defects, reconstruction with half of peroneous longus tendon autograft facilitates postoperative spinal function recovery and pain alleviation, achieves satisfaction with the returning to daily activity and sports, and has few complications.